Sunday

July 5, 2015

July 5, 2015

Total # Posts: 11,301

**math**

Please refrain from starting a new thread when information refers to a previous thread.
*June 15, 2015*

**math**

"last one is $300" So you would write a table as follows Date description amount Balance -......bal.brought fwd - 2000 Jan 2...deposit 500 2500 Jan 10..Alex co. 600 1900 Jan. 16 Angels co. 300 --?-- So you can calculate the final balance on the last line.
*June 15, 2015*

**math**

It is an optimization problem. Here are some steps to solve the problem: 1. define variables (values that are to be found). 2. Reread the question, and translate each constraint into an inequality. 3. Graph the constraints and select the feasible region, using the variables as...
*June 8, 2015*

**math (incomplete)**

There are critical characters that are not legible in the post. Please amend the post, or repost.
*June 8, 2015*

**Math/ASU**

For every child ticket, 2.25 adult tickets were sold. This is the same as For every 4 child tickets sold, 9 adult tickets were sold, for a total of 4*2+9*9=$89. Number of sets of sets (4+9) sold = 520/13=40 Total amount = 40*$89=$3560 Alternatively, using algebra, A=number of ...
*May 29, 2015*

**Geometry**

surface area = 4πr^2 Volume = 4πr^3/3 S/V ratio = 4πr^2 / (4πr^3/3) = 3/r
*May 29, 2015*

**Math**

Base Area = triangle base * triangle height /2 Prism volume = Base Area * height You have been given triangle base: 7 ft triangle height: 4 ft prism height:8.5 ft Apply the above formulas to calculate the volume required.
*May 22, 2015*

**Math- simple polynomials**

Can you explain how you got 4 and 1/9 please. I prefer to see you post the answer, not the letters. This way you have an extra chance of checking your answer.
*May 21, 2015*

**Algebra**

Hint: Reminds me of the Fibonacci numbers.
*May 17, 2015*

**Math**

one light-year is the distance light travels in one year. Light travels at a speed of 3*10^8 m/s. In one year, there are 365*24*60*60 seconds. So one light-year = 3*10^8 * 365*24*60*60 m = 9.461*10^15 m = 9.461*10^12 km (since 1km=1000m)
*May 17, 2015*

**Math**

the value is 7 choose 4, or choosing 4 students out of 7 (order does not count). "7 choose 4" can be evaluated as 7C4 = 7!/((7-4)!4!) = 7!/(3!4!) = 5040/(6*24) = 35
*May 17, 2015*

**Calculus 2**

hints: use the relations: x=rsinθ y=rcosθ which means the left-hand side =x²+y²=r² Also 8sin2θ = 16 sinθcosθ =16(y/r)(x/r) =16xy/r² Equating both sides, x²+y² = 16xy/r² or (x²+y²)² = 16xy =2xy/(x&...
*May 17, 2015*

**Math (Solving Equations)**

No, you do not distribute the absolute value signs. What you did is correct, i.e. keep the absolute value quantity intact, and eventually evaluate the value as either positive or negative. |x-1|=5 means x-1=5 => x=5+1=6 or -(x-1)=5 => x=1-5=-4
*May 17, 2015*

**math**

Discount is calculated by the formula: Discount = Maturity value * discount rate * discount period. Here I assume "face value" is what the bearer receives on maturity. So discount = 2200*0.09*140/365 = $75.95 You can read the following link for more details: http://...
*May 16, 2015*

**Computer science**

Pseudocode is almost like human language input billed_amount; amount_with_tax=billed_amount * 1.09 Total=amount_with_tax*1.15 output total
*May 13, 2015*

**Math**

Exactly, well done! :)
*May 12, 2015*

**Math**

In math, knowing the definition of the terms is key to solving the problem. What you have attempted to find is the mean (or average), not the median. Here the key term is "median", defined as follows: "To find the Median, place the numbers you are given in value...
*May 12, 2015*

**Pre-Calculus (absolute values)**

Knowing the definition of specific math terms helps solving the problem, most of the time. Here the term is invariant point, which is usually called fixed point, defined as follows (Wiki) "In mathematics, a fixed point (sometimes shortened to fixpoint, also known as an ...
*May 12, 2015*

**Physics**

μs determines when skidding will begin. Maximum centripetal force provided by static friction = (μs)mg Maximum speed = v, centrifugal force = mv^2/r At equilibrium, (μs)mg = mv^2/r Solve for v v=sqrt(μs * rg) =sqrt(0.85*215*9.81) =42 m/s approximately
*May 12, 2015*

**To Anono**

Lucina has been giving you excellent and patient help. Please appreciate her time dedicated. If you want correct anwers, you need to do your part by checking the questions/answers that you post. Any typo in the post will give you a right answer to the wrong question. For ...
*May 12, 2015*

**Plane Trigonometry**

This is a very common problem for surveyors to find distances between two objects which they cannot reach. The same principle is used to find difference in heights. Surveyors can do this today because the newer generation of theodolites can measure distance without a prism ...
*May 11, 2015*

**geometry**

factors do not cancel when we add, only when we divide. For example, 2π+5.5π =(2+5.5)π =7.5π or 12πr²+23π =(12r²+23)π
*May 11, 2015*

**math**

Assume decimal digits, so there are 9 non-zero decimal digits [1-9]. The probability that the second digit is 8 is one choice (8) out of 9 possible digits = 1/9. Using conditional probability, Let event of getting (8) = 1/9 so assuming independence of the choice of digits, P(...
*May 10, 2015*

**math**

Use amount = principal * ert where principal = initial investment e=napier's constant=2.7182818284... r=annual rate of interest t=time in number of years Example: 1000$ invested for 3 years at 6% amount = 1000 * e0.06*3 = $1197.22
*May 10, 2015*

**Maths**

Fast method: Ratio of boys to girls = (69-65):(75-69) =4:6 =2:3 Number of boys = 80*2/(2+3) = 32 Standard method: Let x=number of boys (75*x + 65*(80-x))/80 = 69 Solve for x 75x-65x = 69*80-5200 = 320 10x=320 x=32 Answer: there are 32 boys.
*May 10, 2015*

**algebra**

Use Amount = principal * (1+i)^n principal=initial investment number of periods (of 3 months) = 10*4=40 i=interest per period = 3.5%/4=0.00875
*May 10, 2015*

**Linear Functions**

As an example, e=300 means she earns 300 per week flat salary. e=0.05s means she gets paid 5% of weekly sales. If she gets both a base salary and a commission of 5%, then e=300+0.05s Adapt the example to solve the given problem.
*May 9, 2015*

**math**

As a rough approximation, we will assume that the decrease in area is directly proportional to time. 1. Calculate the number of months between September and March = 6 2. Calculate the total decrease in area = (18-3) = 15 million square kilometers. 3. Calculate average decrease...
*May 9, 2015*

**Math**

In math, knowing the definition of related terms can help solve a large number of problems. For example, if we know the definition of price elasticity, we can solve the above problem. Definition: The elasticity is represented in numerical form, and is defined as the percentage...
*May 7, 2015*

**Math**

Start with the anti-symmetry of sine sin(x)=-sin(-x) so sin(-15°)=-sin(15°) Now use cos²(x)-sin²(x)=cos(2x) cos²(x)+sin²(x)=1 Subtract first equation from second: 2sin²(x)=(1-cos(2x)) sin(x)=sqrt((1-cos(2x))/2) Put x=-15° sin(15°) =-sin...
*May 6, 2015*

**university of hartford**

If velocity = v(t), then displacement s(t) = ∫v(t) Use s(0)=6 to determine the constant of integration. For example, if v(t)=3x² then s(t)=∫v(t)=x³+C Given s(1)=4, we have 1³+C=4 => C=3 So s(t)=x³+3
*May 6, 2015*

**probability**

1. correct For the rest, think about: 2 & 3 Probability of two independent events: for two independent events A and B to both happen, the probability is P(A)*P(B) Example: The probability of throwing a 4 from a number cube AND drawing a red card from a standard deck is (1/6)*(...
*May 5, 2015*

**Math**

sx=reflection about the x-axis (x,y)->(x,-y) so (x, 2(x+3)^2-1 ) -> (x, -(2(x+3)^2-1)) = (x, -2(x+3)^2+1) Now apply the translation of 5 units down to get the answer.
*May 5, 2015*

**mathematic**

base radius = r = 5 cm cone height = h = 12 cm Use Pythagoras theorem to find slant height slant height, L = sqrt(5²+12²) =sqrt(169)=13 cm Total surface area = π r²+πrL Substitute numerical values to get numerical answer.
*May 5, 2015*

**Calculus**

When f'(x) > 0, the function is increasing. Conversely, f'(x) <0, function is decreasing. Thus the function is increasing in the interval (-∞,-3], and decreasing on [-3,∞). This makes a maximum at x=-3. Since we do not know anything about f"(x), ...
*May 4, 2015*

**Math-Probability**

Could you please post the whole question in its original form before you make your comments, please? What is not clear is if the audit is selected/done only on those who got a refund, or a selected proportion (1.01%) of all the returns are selected at random for audit. ...
*May 3, 2015*

**Math-Conditional Probability**

Please post the exact original text of the question. We need to examine the wording, even the punctuation to interpret correctly the given information. Confirmation is needed for: - is 85.6% out of the unaudited general population? - Are 49097 and 1342674 the revised ...
*May 3, 2015*

**Trigonometry**

Very true, thanks Steve.
*May 3, 2015*

**Trigonometry**

Many math problems can be solved by understanding the definition of the key term involved. In this case, the key term is the inverse of a (trigonometric) function. From Wikipedia: "In mathematics, an inverse function is a function that "reverses" another ...
*May 3, 2015*

**Math**

When adding polynomials, group like terms (which have identical powers of variables). (8x^2 + x^2) + (- 7x - x + 2x) + (5y - 3y) notice how the x terms were grouped, preserving all the signs. The first group (8x²+x²) would give 9x² with no ambiguity. The same is...
*May 3, 2015*

**statistics**

In a normally distributed random variable, the probability of X≤μ is exactly 0.5, since the normal distribution curve is symmetrical.
*May 2, 2015*

**Math HELP! Ms.Sue**

First you need to be able to interpret the stems and leaf plot (since there are two stems). The two bars enclose the 10's digit, and the numbers to the left of the first bar represent the units digit for soil A, and the numbers to the right of the second bar stands for the...
*May 2, 2015*

**math**

The answer is correct. Don't know what you did until you posted your work.
*May 2, 2015*

**Physics Help Please --- Telescope**

b. Magnification is a pure number (no units) c. When turned around, fe=17, fo=114 M=?
*May 2, 2015*

**Maths(URGENT ANSWER please )**

The series 1 + 4/3! + 6/4! + 8/5! is Σ2k/(k+1)! for k=1,∞ =2Σk/(k+1)! k=1,∞ =2Σ(k-1)/k! k=2,∞ =2Σk/k!-1/k! k=2,∞ =2Σ1/(k-1)! k=2,∞ - 2Σ1/k! k=2,∞ =2Σ1/k! k=1,∞ - 2(Σ1/k!-2) k=0,∞ =2...
*May 2, 2015*

**engineering mechanics**

We don't get to know because we do not have the chance of looking at the numerical values in the diagram that you have in front of you.
*May 2, 2015*

**algebra**

If √N=a√3 then N=a²*3 = 3a² Substitute 3 integer values of a to find 3 possible values of N.
*May 1, 2015*

**conditional probability**

Many basic math problems can be solved by understanding the definition of terms. Conditional probability P(E|F)=conditional probability that event E will occur given that event F has already occurred = P(E∩F)/P(F) Therefore P(F|E)=P(F∩E)/P(E) =P(E∩F)/P(E) since the...
*April 30, 2015*

**probability**

First make a 6x8 table of the possible outcomes (sample space, 48 points). For random throws, each of the 48 points has equal probability (p(i,j)=1/48). a. Expected value of sum of two dice: E[X]=Σ p(i,j)(i+j) i=1,8, j=1,6 Where p(i,j)=1/48, and i+j can be taken from the...
*April 30, 2015*

**maths**

Knowing that one mango costs $2.40, we can set it up as 2A+2(2.40)=5A+2.40 and solve for A.
*April 28, 2015*

**Math 222**

A perfect square has the form (y+a)²=y²+2ay+a² If you compare with y²-18y+a² you can find a by equating the second term and solving for a: 2ay=-18y
*April 27, 2015*

**Chemistry**

* molar mass
*April 27, 2015*

**Chemistry**

The N:O ratio can be obtained by dividing the % mass by the respective atomic masses, namely N:O = 30.4/14 : 69.6/16 = 2.17:4.35=1:2 Use the 5.25g sample and the ideal gas law to find the molecular mass and hence the composition.
*April 27, 2015*

**Chemistry**

Convert the volume to V at 1 atm. At 25°C, the molar volume is 24.465 L. Use proportion to find the molar mass, M 0.642/V = M/24.465
*April 27, 2015*

**statistics**

The sample space has 36 equiprobable outcomes. You can enumerate the successful outcomes and divide by 36. Here's another approach: Success of at least one odd number means that a failure is when both are even. Probability of a failure is (1/2)*(1/2)=1/4, we gather that ...
*April 26, 2015*

**Physics**

From the given information, we deduce that It takes 4.184 J/g * 1000 g = 4184 J to raise the temperature of 1 L of water by 1°C. Assuming that all 1000J of heat are absorbed by the 1 L of water, then by proportion, the temperature increase equals 0.239°C. 1°C * (...
*April 26, 2015*

**STATISTICS**

See earlier Q & A.
*April 25, 2015*

**statistics**

Yes, you can find the answers if the distribution curve is known. The standard normal distribution curve has an area of 1.0 under the curve. To convert a curve with mean 100 and SD=15 to the normal curve, we use Z(X)=(X-μ)/σ which means X=σZ(X)+μ where &sigma...
*April 25, 2015*

**Math**

I agree.
*April 25, 2015*

**PHYSICS answer check**

Please show equations or calculations used in obtaining your answer so that we can help you check your work.
*April 25, 2015*

**DISCRETE MATH**

The finite population has 100 devices, out of which 80 are non-defective. At each draw, both the total number devices and the number of non-defective device decrease, we have the running probabilities as: {80/100, 79/99, 78/98, 77/97, 76/96} the product of which give 0.31931, ...
*April 24, 2015*

**numerical methods**

Correction: V(h) should read: V(h)=π(3h²R-h³)/3 =πh²(R-h/3)
*April 23, 2015*

**numerical methods**

When the tank has 6.3 ft of oil, the dipstick will be wet by 6.3 feet if it is inserted vertically to the very bottom of the tank. The radius of the surface of water at height x in a sphere of radius R is given by r(x)=sqrt(R^2-(x-R)^2) By integrating r(x) with from 0 to ...
*April 23, 2015*

**chemistry**

molar mass of CH3COOH =(12+3+12+16+16+1) =60 mass of acetic acid in 250 mL of 0.26M =(250/1000) L * 0.26*60 = 3.9 g
*April 15, 2015*

**More math**

9C4=9!/((9-4)!4!) Use your calculator to work that out.
*April 15, 2015*

**Math**

nPr=n!/(n-r)! 6P2 =6!/((6-2)!) =?
*April 15, 2015*

**Simple math.**

n! = n(n-1)(n-2)...(3)(2)(1) for example, 3! = 3*2*1=6 You can use the ! or factorial function of your calculator to find the answer for 5!. You can also calculate the products long-hand.
*April 15, 2015*

**maths**

clarification: Hint: DC is not parallel to AB unless ∠DAB is 90°.
*April 15, 2015*

**maths**

It is an excellent exercise to follow instructions in order to draw a diagram. I would let you do just that, and at any step the statement is incorrect, it is the required answer. Hint: DC is not parallel to AB.
*April 15, 2015*

**physics - good catch!**

Haha! At least someone noticed that! Yes, in my days, slide-rules were not accurate enough, and survey calculations were done using 7-figure (log and trig) tables which were packed in a volume (I still have one!) thicker than today's calculus textbook. That taught me how ...
*April 15, 2015*

**basic trigonometry**

I hope you mean the ski track along the mountain is 235 m long. The mountain can be represented by a right triangle with the two legs horizontal and vertical, and where the angle of elevation is 35°. The ski track is the hypotenuse (C), and if the horizontal leg (B) and ...
*April 15, 2015*

**math-need figure**

To ollie: The question is meaningless without the accompanying diagram. You could post a link to the diagram, or you can describe what the diagram looks like. Sorry that we cannot go further without the rest of the required information.
*April 15, 2015*

**linear algebra**

Use the properties of linear transformations: 1. T(A+B)=T(A)+T(B) 2. T(kA)=kT(A) then let A=[1,1], B=[-1,1] and T(A+B)=T(0,2)=[-2,1]+[3,2]=[1,3] => T(0,1)=[1/2, 3/2]=P and T(A-B)=T(2,0)=[-2,1]-[3,2]=[-5,-1] => T(1,0)=[-5/2, -1/2]=Q So (a) L(-1,5)=-P+5Q =-[1/2,3/2]+5[-5/2...
*April 15, 2015*

**statistics**

7 choose 5 = 7C5 = 7!/((7-5)!5!) = ? ! means factorial.
*April 15, 2015*

**statistics**

probability is constant and independent of trials. trials are Bernouli, i.e. either success or failure. Number of trials is known. All this point to the binomial distribution where P(k successes out of n) =nCk p^k (1-p)^(n-k) p=probability of success of each independent trial=...
*April 15, 2015*

**physics**

Solve for n in PV=nRT 2.79*10^5(3.66)=n×8.314462175×(19.8+273.15) to get 419 moles (3 sig. figures) and similarly solve for P in P(7.20)=419.235(8.314462175)(28.5+273.15) to get 1.46*10^5 (3 sig. figures) Your approach is correct, but cannot tell where you got ...
*April 14, 2015*

**physics**

131 m. :)
*April 14, 2015*

**Mechanical Principles**

corrections. I forgot to multiply F(x) by x in the integral. So T should read less than 6 kN instead of 10.
*April 13, 2015*

**Mechanical Principles**

We have an increasing hydrostatic pressure varing from zero at water surface to the depth of the water, which exerts a varying force on the gate. The tension on the cable can be obtained by taking moments about the hinge of the gate (at the bottom). Let H=height of gate (where...
*April 13, 2015*

**CIRCUITS**

Resistance across resistors in series = R1+R2+R3 Voltage across each resistor is proportional to the fraction of each over the total. For example, resistors R1=2,R2=1,R3=3, ohms are connected in series and subject to a voltage of 12 volts, Resistance of resistors in series R=...
*April 12, 2015*

**Math**

For a rectangle, area = length × width perimeter = 2(length + width). Example: for a rectangle with length = 5 ft width = 3 ft area = 5×3 = 15 square feet perimeter = 2(5+3) = 16 feet
*April 12, 2015*

**maths**

Volume of a cube, Vc = (side length)³ Volume of a cylinder Vcy= πr²*h where h=length/height of cylinder r = radius of base = diameter of base /2 If their volumes are equal, then Vcy = Vc πr²*h = side³ Solve for h.
*April 11, 2015*

**geometry**

Height / distance = tangent so distance = height / tangent = 28 ft / tan(11°) = ...
*April 10, 2015*

**maths**

SI=simple interest formula is Interest = Principal * annual interest rate * number of years = 225 * 0.16 * 3.75 = 135 Add interest to principal to get final repayment amount.
*April 10, 2015*

**Combinations-Math**

74 is correct.
*April 10, 2015*

**physics. urgent answer please**

F1=10 N at 60° F2=15 N at 0° Use x- and y-components method: x-component Fx=F1*cos(60)+F2*cos(0) =20 N y-component Fy=F1*sin(60)+F2*sin(0) =8.660254 N Resultant, R= √(Fx²+Fy²) angle, θ = atan2(Fy, Fx) Hints for checking your answer: 20 N < R &...
*April 10, 2015*

**French**

The words are in the right places and the right form, except for #2 where the number does not agree with the definite article "le". It should be either l'assiette (sing., more probable) or les assiettes (plur.) Not knowing the instructions nor the purpose of the ...
*April 9, 2015*

**linear algebra urgent**

http://www.jiskha.com/display.cgi?id=1428173198 Also, remember that u3=u3-p(u1,w3)-p(u2,w3) where p(u1,w3) is the projection of w3 on u1, etc.
*April 9, 2015*

**linear algebra urgent**

see other post
*April 9, 2015*

**Math**

Assuming that strawberry on vanilla is considered the same flavour as vanilla on strawberry, i.e. order of the two scoops doesn't count, then there are 30C2 possible flavours, and 3 cones for a total of n=3(30C2) possible ice creams. For an order of 12 different ice-creams...
*April 9, 2015*

**math**

If you could post the question exactly as you were given, it would be possible for us to understand what you need. Especially in math, paraphrasing tends to lose important information.
*April 9, 2015*

**maths**

If the GP has its third term as 9 times its first term, then the sequence is a, ar, ar² where a is the first term, ar is the second term, etc. This means that ar²/a = r²=9, or r=3. Similarly, the fifth term divided by the second term should be a^4/a^1 = a^3, or ...
*April 9, 2015*

**Math**

The quadratic formula assume the equation to be: ax²+bx+c=0 (i.e. all terms are on the left-side of the equation). Rearrange the equation to be 3x²+4x-6=0 and try again. You do not need a graphing calculator to find the zeroes. Either by hand, or a regular calculator...
*April 9, 2015*

**Trigonometry (identities) (last help needed)**

Typically with simplification like these, you would convert all functions into sine and cosine, and simplify from there on. Use sin²x+cos²x=1 whenever appropriate.
*April 9, 2015*

**Trigonometry (identities ?)**

Trigonometric identities involve an equal sign with a different expressions on either side. So it's not clear what exactly you require in your questions. Do you need to simplify the expressions? I suggest you check for typos as well as I do not see what β has to do ...
*April 9, 2015*

**linear**

To find W⊥, you can use the Gram-Schmidt process using the usual inner-product and the given 5 independent set of vectors. Define projection of v on u as p(u,v)=u*(u.v)/(u.u) we need to proceed and determine u1...u5 as: u1=w1 u2=w2-p(u1,w2) u3=w3-p(u1,w3)-p(u2,w3) u4=w4-...
*April 9, 2015*

**CALCULUS**

f(x)=9x³-4x^5 F(x)=∫f(x)dx=(9/4)x^4-(4/6)x^6+C Given F(1)=0, solve for C and hence find F(4) F(1)=(9/4)1^4-(4/6)1^6+C=0 => C=(4/6)-9/4=(8-27)/12=-19/12 => F(x)=(9/4)x^4-(4/6)x^6-19/12 Find F(4)
*April 9, 2015*

**Math (Help please)**

Rows are horizontal, numbered from top to bottom, columns are vertical, numbered from left to right. For example, element at row 1 column 3 is equal to 6, element at row 2 column 4 is equal to 0.
*April 9, 2015*

**physics - work, power**

We do not support LaTeX here, but you can use / for division, and unicode symbols for special characters. Power = work / time work = Force * distance speed = distance / time force * speed = force * distance / time I believe the four equivalences are sufficient for you to get ...
*April 9, 2015*

**READ - to Sarah**

Well said! Thank you!
*April 9, 2015*