Monday

August 3, 2015

August 3, 2015

Total # Posts: 11,302

**math**

Right, there was a typo! Thought I corrected it. Thanks Steve! Should read: g*62+(75-g)*56=75*58
*March 27, 2015*

**math**

Let g=number of girls, and assuming all data given are exact (i.e. no rounding involved), then g*62+(75-g)*58=56 Solve for g.
*March 27, 2015*

**physical science**

All free-falls on earth starts at g (9.8 m/s²) if initiated near the surface. At high elevations, g is slightly reduced because of the greater distance from the centre of the earth. Subsequently, as velocity is substantial, air-resistance plays an important rôle in ...
*March 27, 2015*

**Astronomy**

Hint: Escape velocity =√(2GM/r) G=gravitational constant M=mass r=radius When mass is doubled, replace M by 2M, similarly for r. For further reading, see for example: http://en.wikipedia.org/wiki/Escape_velocity
*March 26, 2015*

**Math**

337 is her total score, and 84.25 is her current average up to the fourth test. If she ended up with a grade of 90, that means her total score (for all five tests) is 5*90=450. So what did she score in the final test?
*March 26, 2015*

**algebra**

Hints: here are the possible situations: When discriminant is negative: 2 imaginary roots When discriminant is a positive perfect square, such as 1, 4, 9, 16... and all coefficients are rational: 2 real, rational roots When discriminant is zero, and either coefficient a or b ...
*March 26, 2015*

**Math**

Use n instead of 18% in your first and second calculations. a. 500*n%=5n net receipt=500-5n = 500(1-n/100) b. 100%-n%=(100-n)% net receipt = 500(100-n)% = 500(1-n/100) Since a and b are the same, so the two calculations are equivalent for any value of n.
*March 26, 2015*

**math**

Hints: Actual Length = model length * scale Actual area = model area * scale² Actual volume = model volume * scale³
*March 26, 2015*

**algebra II**

Use the law of logarithms: log(a)+log(b)=log(ab) => log(x+2)+log(x-3)=log(x+29) log((x+2)(x-3))=log(x+29) => (x+2)(x-3)=x+29 x²-2x-35=0 (x-7)(x+5)=0 Solve for x, and reject any solution which will result in a negative argument to the log function.
*March 26, 2015*

**computer programming**

Store three arrays: String[] model={"Chevrolet",....}; double[] dailyRate={50,85,53,60,60,70}; double[] milageRate={0.27, 0.45,....0.40}; int nModel=0; int milage=0; double cost; then present a menu for user to choose from, remembering that model[0]="Chevrlet&...
*March 26, 2015*

**Math**

Yes, that's what I got, and here's how: 1125(4*.262-1)=54
*March 26, 2015*

**Math**

Yes, you're right. I misread the 80% as the copayment. Most health insurance companies that I have seen have annual deductibles, which I assumed. Here I interpreted that the $300 was a previous payment, which exceeds the annual deductible. However, since no mention was ...
*March 26, 2015*

**Math**

He paid $300 in copayments, so that means that the deductible no longer applies on subsequent payments. Out of the $2300 in hospital bill, he has to pay the copayment of 80% = 2300*0.80 = $1840 added to the previous copayment, he paid a total of 1840+300 = $2140 Please explain...
*March 26, 2015*

**phy**

0°K------------273.15°K 0°K-------------0°C--------232°C Conversion from °C to °K °K = °C + 273.15
*March 26, 2015*

**physics**

t = time of free fall = 35 s Horizontal distance = horizontal speed × duration of free fall For the vertical component of free fall, Vyi=initial vertical velocity = 0 a=vertical acceleration = -g = -9.8 m/s² ΔY = vertical position change ΔY = Vyi(t)+(1/2...
*March 26, 2015*

**Physics**

Yes, you have figured it out. On the other hand, extraneous information is present in everyday real problems. In solving problems, it is a necessary skill to pick out relevant information.
*March 26, 2015*

**Calc**

Given a polynomial function in t where I(t) = 0.00009045t5+0.001438t4−0.06561t3+0.4598t2−.6270t+99.33 We need to find the extrema for 0≤t≤10. Steps: find first derivative I'(0), equate to zero. Solve for the zeroes which correspond to the extrema, say t1 ...
*March 26, 2015*

**Physics**

Whole circumference of a circle of radius r = 2πr. 1 km/h = 1000/3600 m/s Distance = speed × time.
*March 26, 2015*

**physics/chemistry**

Assuming the flask was filled with propane only, and propane approximately closely an ideal gas at the given temperature, you can use the ideal gas equation PV=nRT where R=8.314 J-K-1mol-1 P=pressure in pa V=volume in m³ n=number of mols (pure number) T=temperature in &...
*March 26, 2015*

**Calculus**

Try reading the following in compensation for the quick lesson. http://www.economicshelp.org/blog/7019/economics/examples-of-elasticity/ and for equations/formulas: http://study.com/academy/lesson/the-elasticity-of-demand-definition-formula-examples.html p=price=$2 q=quantity ...
*March 25, 2015*

**Computer science**

The logic looks correct except for one minor logic error in: sum=sum+(i*rem); which should read sum=sum+i*r; You need to make sure the statements execute correctly in Matlab syntax. For example, an integer division can be written as dec=dec./2; or dec=idivide(dec,2); Also, be ...
*March 25, 2015*

**physics**

We will take velocity and distance as positive upwards, and distance = 0 at the bottom of the cliff. Use Distance = Vi*t-(1/2)gt² For the stone thrown upwards, X1(t)=9.33t-(1/2)gt^2 For the stone thrown downwards, X2(t)=5.28-9.33t-(1/2)gt^2 When they meet, X1(t)=X2(t) and...
*March 25, 2015*

**Math**

Subdivide the shape into known sub-figures. Sum the areas of all the sub-figures.
*March 25, 2015*

**math is my answer correct**

Your answer is quite close. I get 337.66. If you have been copying intermediate answers to 4 figures, that would make the difference. Try to use the calculator memory instead of copying down intermediate answers.
*March 25, 2015*

**physics**

Vi=29.2 m/s θ=31.7° Vxi=Vi cos(θ) = 24.844 m/s Vyi=Vi sin(θ) = 15.344 m/s since Vy(t)=Vyi-gt so at the maximum, Vy(t)=0, or Vyi-gt=0 => t=Vyi/g The optimal (best) horizontal distance would therefore be the horizontal distance travelled during this time...
*March 25, 2015*

**French**

Subjunctive mood should be used when any of the following is involved in the situation: - doubt, - wish - desire - emotions So that applies to 1A and 1B. The present tense of the subjunctive mood for the two verbs are: You can use the Bescherelle or Internet to look up the ...
*March 25, 2015*

**System ?**

You can set up a system of equations: let x=number of 2-point questions, then 40-x = number of 3-point questions. 2(x) + 3(40-x) = 100 Solve for x. Or you can solve mentally as follows: If all questions are worth 2-point, then the total = 2*40=80 points, or 20 points too few. ...
*March 25, 2015*

**Math Check**

The answer is basically correct, except for an error of sign in one place which I think you will spot readily. Also, when there is multiplication following division, insert parentheses to express clearly what is needed. For example, 6/4y should be interpreted as (6/4)y (left-...
*March 25, 2015*

**math,Computer**

Are you already familiar with linked lists? We assume A and B are singly linked lists, i.e. linked in the forward direction only. To attain the end of a list, the node pointer must traverse every node from head to tail. The number of operations is therefore n, where n=size of ...
*March 25, 2015*

**math,Computer**

I interpret this as: if (A==φ)A|B == B else A|B = Ha|Tab But then we're defining A|B using Tab, which is the tail of A|B. Sounds to me a circular definition. Can you please clarify the definition, or give your comments?
*March 25, 2015*

**maths**

Time to reach bottom = t s distance 44 m= (1/2)gt^2 where g=acceleration due to gravity = 9.8 m/s² => t=sqrt(2*44/g)=2.997 s Subtract this time from 3.12 seconds will be the time needed for sound to travel 44 m. Use Distance=speed × time to find speed of sound.
*March 25, 2015*

**French**

If I say "con-" is a common prefix, does that help?
*March 25, 2015*

**math**

"...students having the best score..." ? 85/100 has a range of [84.5%,85.5%] 170/200 has a range of [84.75%,85.25%] I would take the better of the worst case, namely, candidate with a least score of 84.75%. In practice, I would decide by a final interview.
*March 24, 2015*

**statistics**

P(lose once) = (15-2)/15 = 13/15 = (13/15)1 by the multiplication rule: P(lose n times) = (13/15)n
*March 24, 2015*

**Math**

Total reading time: 8/9 World news: 1/4 of 8/9 = (1/4)*(8/9)=2/9 Remaining time = 8/9 - 2/9 =(8-2)/9=6/9 Half of remaining time = (1/2) 6/9 = 3/9 =1/3 h.
*March 23, 2015*

**Advanced Algebra**

Think of how many ways you can choose a chairman (10), vice-chairman (9 remaining people), secretary(8), treasurer (7). Multiply them together using the product rule, and the product is 10*9*8*7 =10*9*8*7*6*5*4*3*2*1/(6*5*4*3*2*1) =10!/(10-4)!
*March 22, 2015*

**math**

where μ represents the frequency of occurrence (success) within a given time period (week). In this case, failure is considered "success". so μ =3 "successes" / 20 weeks =3/20 By definition of the Poisson distribution, P(x;μ)=e-μμx/x! where x...
*March 21, 2015*

**math**

The outcomes are X={0,1,2,3}, with probabilities P(x)=(1/8)x!/(3!(3-x)!) The mean, or expected value E[X]=ΣxP(x) =Σ(0*(1/8)+1*(3/8)+2*(3/8)+3*(1/8)) =12/8 =3/2
*March 21, 2015*

**French**

The apostrophe would be used when some letter is dropped, and in some cases only. For example, il faut que elle... would be shortened to il faut qu'elle... because phonetically it is difficult and unpleasant to read the two vowels one after another. It is perfectly ...
*March 20, 2015*

**French**

A. Your answer is very close, except that the qu' is part of the Est-ce que...., and should be eliminated. The question reads: Boit-elle un apéritif? Note: (bois, bois, boit, buvez, buvez, boivent) However, the auxiliary verb vouloir must be maintained, so the ...
*March 20, 2015*

**math(Discrete)**

Translation into English: For all x which are integers, there exist y and z which also are integers, such that x=5y+7z. Is the above statement true? Give it a few tries: triplet means (x,y,z) (0,7,-5) is a solution (1,10,-7) is a solution (2,-1,1) is a solution (3,2,-1) is a ...
*March 19, 2015*

**French**

The French expression "venir de" is a special tense that means "just" (in temporal sense), or "a short while ago". Je viens de terminer mon travail (I just finised work). Il vient de me parler au téléphone. (He talked to me on the ...
*March 19, 2015*

**Math Answer Check**

Yes, that is correct, but try to understand why you do that by studying the unit circle.
*March 18, 2015*

**Math Answer Check**

cotangent: 1 secant: negative square root 2 cosecant: negative square root 2 *sin: square root 2 / 2 *cosine: square root 2 / 2 tan: 1 The terminal side lands in the third quadrant, where only tangent (and cotangent) is positive. So sine (cosec) and cosine (sec) are all ...
*March 18, 2015*

**Algebra 2 (DIVIDEPOLYNOMIALS)**

Here's a link for long division. http://www.purplemath.com/modules/polydiv2.htm Quite frequently we use synthetic division, with less writing to do: http://www.purplemath.com/modules/synthdiv.htm Hint: the given problem leaves no remainder.
*March 18, 2015*

**Math**

A reference angle is the positive acute angle between an angle and the horizontal axis. For the different possible cases, see: http://www.mathwarehouse.com/trigonometry/reference-angle/finding-reference-angle.php
*March 18, 2015*

**Math**

The first step is to convert one equation into the same form as the other. Most of the time, we would convert the second to the form of the first, i.e. x=-2-(2/3)y (parentheses added according to rules of BEMPAS, or PEDMAS. x+2=-(2/3)y Multiply by 3 on bothe sides 3x+6=-2y 6=-...
*March 18, 2015*

**math**

If Esi is always behind Becky, we have only 4 independent choices for each position. So for the first position, there are 4 choices, for the second, 3 choices left, then 2, then 1. The number of permutations is the product of the 4 numbers.
*March 18, 2015*

**math**

I'll solve the first one, and the second one can be solved similarly. (n-2)!/(n-3)! =(n-2)(n-3)!/(n-3!) =n-2 therefore n-2=15 => n=17 Check: (17-2)!/(17-3)!=15!/14!=15*14*...*1/(14*13*..*1) =15 checked ok.
*March 18, 2015*

**French, foreign language**

Don't know if you have read Ms Sue's and my comments, but here's the link: http://www.jiskha.com/display.cgi?id=1426621380 Is the exercise corrected by hand or a computer? With a computer, you need to do exactly what it expects. I don't understand how it/he/she...
*March 18, 2015*

**probability**

9 10 11 `1 ******** ******** There is an overlap between the two periods. Since each individual function is uniform, the resulting f(x) is a step function such that: f(x): (1/4)/2 = 1/...
*March 18, 2015*

**Calculus AB: Area Between Curves**

hints: steps: 1. find the equation of the tangent line. The slope m of the line equals f'(-1), and passes through (-1,f(-1))=(-1,4)=(x1,y1). The equation of the line is then y-y1=m(x-x1), or g(x)=m(x-x1)+y1 Draw a sketch of f(x) and g(x) for your own information. 2. Find ...
*March 18, 2015*

**Cal state**

Number of seats in first row = 26 Number of seats in last row = 26+30-1=55 We can find the sum using Gauss's method: 26+27+28+.....+54+55=x 55+54+.....+28+27+26=x Add the two rows 81+81+.....81 (30 rows) = 2x 30*81 = 2x x=1215 seats
*March 18, 2015*

**Maths**

Yes, that is correct.
*March 18, 2015*

**Maths**

Given: S:M:L = 16:23:20 Total = £1180 Actual amounts for each S:M:L = (£1180/(16+23+20)*(16:23:20) =£(320:460:400) Marvin takes out £100, and Lucy puts in £x, so new ratio (8:9:12) = (320:360:400+x) If we multiply the left-hand side by 40, we get...
*March 18, 2015*

**Math**

Cost per litre = $x Number of litres bought = 500/x Number of litres sold, q = 500/x-5 new sale price per litre = x+2 Total revenue = q*(x+2) = 540 so (500/x -5 )*(x+2) = 540 Solve for x (cost of paint per litre) I'll get you started: Multiply both sides by x (500-5x)(x+2...
*March 18, 2015*

**Math**

Factor by grouping: 3x^2+5xy-2y^2 =3x²+6xy -(xy+2y²) =3x(x+2y)-y(x+2y) =(3x-y)(x+2y) =0 So either (3x-y)=0 or (x+2y)=0 Hence find the two possible values of x/y.
*March 18, 2015*

**math**

25% of a class of 40 means there are 0.25*40=10 girls. Let x new girls joined the class. total number of girls = 10+x total size of class = 40+x Given girls now make 40% of class, then (10+x)÷(40+x) = 0.40 Cross multiply and solve for x. Alternatively, solve by guess ...
*March 18, 2015*

**Math**

The future value FV can be calculated by summing payments and simplification using factorization: FV = S(1+(1+r)+(1+r)^2+...+(1+r)r^(n-1)) =S((1+r)^n-1)/((1+r)-1) =S((1+r)^n-1)/r FV=future value S=Semi-annual payment r=interest per period (6-months) n=number of periods (6-...
*March 18, 2015*

**Algebra**

fourth term: ar^4 7th term: ar^7 Let common ratio = r then 7th term / 4th term = ar^7/ar^4 = r³ therefore r = cube root of r³ Fifth term = fourth term * r
*March 18, 2015*

**math**

The first step in evaluating a limit would be to substitute the limiting value into the expression. If it evaluates to a valid number, that is the limit. Example: limit x->1 x²/x =1²/1 = 1 Since sinx/tanx + tanx.sinx ≡ 1/cos(x) so the limit is 1/cos(0)=1.
*March 18, 2015*

**Math**

Solve for x in 1500+0.04x=5000
*March 18, 2015*

**Math - 7th grade (repost)**

The number of CD's between Q1 and Q3 should be half of the total number of CD's. From the plot, you will not know how many cost less than $14.6, but since Q1 is 14.6, there are at most one quarter of the number of CD's cost less than $14.60. (One quarter of 12 CD&#...
*March 18, 2015*

**Sum and Difference**

Sum and difference problems are solved as follows: Larger number = (sum+difference)/2 Smaller number = (sum-difference)/2 So 1/p = (4+3/2)/2 = 11/4 p = 1/(11/4) = 4/11 I will leave it to you to do the smaller number (1/q).
*March 18, 2015*

**maths**

We are given x²+y²=137 (x-y)=7 this means 49=(x-y)² =x²-2xy+y² =x²+y²-2xy =137-2xy From 49=137-2xy can you solve for xy? The longer way: equation 1: x-y=7 equation 2: x²+y²=137 Now solve the non-linear system in x and y.
*March 18, 2015*

**Math**

Use law of exponents (ax)^b = a^b × x^b y=kx^3 y1=k(1.5x)³=k(1.5^3)x³=3.375kx³=...
*March 18, 2015*

**math**

There is an ambiguity in the question to be clarified about the interest rate. Generally annual interest is quoted. The wording of the question casts a doubt as to 7.2% is monthly or annual interest. Considering that 86.4% annual interest is illegal in some countries, 7.2% ...
*March 18, 2015*

**Math - 7th grade**

See later post
*March 17, 2015*

**Math**

You're welcome. Also note a correction is required: 0.02/5 = 0.004/1 < 0.01=1%
*March 17, 2015*

**Math**

Convert the given fraction to an equivalent fraction with either 1 or 100 as the denominator. We know that 1% = 1/100 = 0.01/1 So say, 0.2/5 = 0.004/1 < 0.01=1% 2/500 = 0.4/100 < 1/100 = 1% etc.
*March 17, 2015*

**Repost, see previous discussions**

http://www.jiskha.com/display.cgi?id=1426619198
*March 17, 2015*

**French, foreign language**

Yes, you need to correct the sentences where the verb and complements do not agree. "Ce sont" is followed by a noun in plural, and "C'est" is followed by a singular noun. Examples: Ce sont des carottes. (Ce sont....plural) C'est un hamburger. (C'...
*March 17, 2015*

**Math Help Me Please**

Ouch! question says "Determine which ordered pair is not a solution of "
*March 17, 2015*

**Math Help Me Please**

substitute x (first number in parentheses) into the right-hand side of the equation and check if the value equals y (second number in parentheses). For example, let's check (9,-48) which is not taken from the choices: -5(9)-4=-45-4=-49 but -49 does not equal -48, so (9,-48...
*March 17, 2015*

**Math**

Question says: If not, then you lose your discount and you pay a 20% premium on the usage outside of that time. Check that you have calculated without the 15% discount.
*March 17, 2015*

**Math**

Since usage is greater outside the prescribed period, there will be a 20% premium for those kW-h. Can you please show us how you got $51.08?
*March 17, 2015*

**Vectors**

Yes, b is correct. Your method works well without having to memorize formulas. If the equations had been in the slope intercept form: y=-x+8 and y=-x then you could also calculate using distance = y-intercept difference / &radic(1²+(-1)²) =8/√2 =4√2
*March 17, 2015*

**Vectors**

Actually, the expression is the expanded form of (x+2)(y-3)=0 which by the zero-product property means x+2=0 => x=-2, or y-3=0 => y=3, or both of the above. So yes, (a) is correct.
*March 17, 2015*

**Algebra 2**

If you are working on polynomials, then binomial is a polynomial with 2 terms, for example, (x+4) is a binomial, or (x³ - 2x²) is a binomial. The first example is a binomial with a degree of 1 (highest power of the variable), and the second is a binomial of degree 3...
*March 17, 2015*

**physics**

The parallelogram of forces yields a triangle with vectors 10,15 and 20. where 20 is the resultant. The angle between the two vector is the supplement of the angle (between vectors 10 and 15) solved by the cosine rule. Draw the parallelogram of forces to understand why it is ...
*March 17, 2015*

**physics**

If the quarter circle has the radii horizontal and vertical, the difference in height equals the radius=1.6m. Neglecting friction and other dissipative forces, then conservation of energy holds, and so KE+PE=0,or (1/2)mv^2 + mg(h-h0)=0 Solve for v where h=0, h0=1.6m and g=9.81...
*March 17, 2015*

**math**

Very often the phrase "of the" means multiply. So he packed 1/3. 1/2 "of the" 1/3 were shipped, this means (1/2)*(1/3) = 1/6 were shipped.
*March 17, 2015*

**Do you have a diagram?**

It is not clear to me how M1 and M2 are related, are they linked vertically by a string, are they released at the same time?
*March 17, 2015*

**Vectors**

To Sara: I got 5/√2 as well. Perhaps it is time to check if there are typos in the question or the answer. Also, to print s∈R, you can write s & i s i n ; R, but skip the spaces.
*March 17, 2015*

**Physics**

Anne throws a ball horizontally... so the problem reduces to a free-fall over 50m. The equation Dy=-50m = V0t+(1/2)gt^2 will let you solve for the time to hit ground, and where v0=initial vertical velocity = 0, and g=acceleration due to gravity = -9.8 m/s² During this ...
*March 16, 2015*

**calculus trigonometric substitution**

You're ok so far. You only need to convert sin(u)cos(u)/54 back in terms of x, which should be x/(18x²+162). You can start by sin(u)cos(u)/54=cos^2(u)tan(u)/54 =3tan(u)/[162(sec²(u)) =...
*March 16, 2015*

**EES**

Hint: think of what you find in the kitchen.
*March 16, 2015*

**computer applications**

It would be much easier for you to open a spread sheet and try it out. I suggest you do some practical work because it will help you understand how it works, and it will help you recall the procedure in the future.
*March 16, 2015*

**Vectors**

Let's check: r1=(3,2,-1)+s<1,1,1> When s=0, r passes through the point (3,2,-1). Now check the product of the two direction vectors: <1,1,1> dot <1,1,-2> =1+1-2 =0 So the two lines are perpendicular and r1 satisfies the required conditions. Note: multiple...
*March 16, 2015*

**engineering**

Stress=σ=Force/Area Strain=ε=σ/E Change in length = ε*Length. Useful conversion factors 1 GPa = 10^9 Pa 1 kN = 10^3 N 1 m = 1000 mm Try to do calculations in standard units, namely kg, m, s.
*March 16, 2015*

**programming**

You can work on the flow-chart based on a pseudocode such as: enter ID, ID enter number of policies sold, N if N > 25 print ID, N endif
*March 16, 2015*

**maths**

1 pascal = 1 N/m² 1 MPa = 10^6 Pa Stress = Force /area, all in appropriate units. = 91*10^3 N / (π0.030²/4) m² Evaluate and convert to MPa.
*March 16, 2015*

**engineering**

1. find average acceleration, a Vi=0 S=(1/2)at^2 139 m =(1/2)a(8.7²) a=3.6729 m/s² 2. Find work done, W a. using F=ma, W = F*S = ma*S where m=1100 kg, S=139 m, a=3.6729 m/s² or b. using energy (neglect loss) final velocity, Vf = at where t=8.7 s final energy =(1...
*March 16, 2015*

**Math**

If we select 6 out of 300 subjects, we can assume that the probability remains approximately constant, thus use of the binomial distribution is applicable, where n=6 p=0.58 bin(6,0.58, 3) =C(6,3)*0.58^3*0.42^3 =0.2891 approximately To be more precise, we calculate the ...
*March 16, 2015*

**stats**

The question satisfies requirements for a binomial distribution, where n=10 p=1/2 Probability of r girls out of n =P(G=r) =(n, r)p^r (1-p)^(n-r) where (n,r)=combination n choose r = n!/(r!(n-r)!) For at least 2 girls out of 10, P(G>=2)=1-(P(G=0)+P(G=1)) 1-(1)(1)(1/1024)-(10...
*March 16, 2015*

**Math**

Expected value is the sum of the product of all possible outcomes and the respective probability. Example of rolling one six-sided die: Payout equals the number appearing on top face. expected value = 1*1/6+2*1/6+3*1/6+4*1/6+581/6+6*1/6 =3.5
*March 16, 2015*

**Trigonometry**

set sin²(x) = 1-cos²(x) 16(1-cos²(x))=16-8cos(x) and substitute c=cos(x) 16c²-8c=0 c(2c-1)=0 c=0 or c=1/2 Find all solutions for c=0 in [0,2π) and all solutions for c=1/2 in [0,2π). Substitute back the solution and check that they are valid.
*March 16, 2015*

**Math**

Tia, You may or may not realize that here there are tutors who answer 50 to 100 posts a day on a voluntary basis just in order to help students. Any repeated post may get read 8 times by 8 different tutors, and worse, could also end up with a duplicate answer which you may not...
*March 16, 2015*

**statistics**

To get the first number right is 1 out of 31 choices. For the second number, there are only 30 choices (five different numbers)... So the probability of getting all five numbers right would be: (1/31)(1/30)...(1/27).
*March 16, 2015*

**calculus**

Calculus question: Let x=length remaining below winch. and ρ=mass density Work done winding up a length of dx is equivalent to bringing the length dx up by a distance of x, i.e. dW=ρg xdx Integrate W=ρg∫xdx from 0 to L =ρg L²/2 Physics question: ...
*March 16, 2015*