Sunday

January 25, 2015

January 25, 2015

Total # Posts: 10,888

**maths**

obtained by adding the two vectors: (18,0)+(3cos(40),3sin(40)) =(18+3cos(40), 3sin(40)) =(x,y) The resultant speed R is obtained by |R|=sqrt(x²+y²)
*June 20, 2013*

**Math**

Let distance be D km, and the current be C km/h His speed is 8 km/h in still water. So his speed upstream is D/3.25=8-C and downstream, D/1.5=8+C Cross multiply each to get D = 3.25(8-C) D=1.5(8+C) Solve by comparison 1.5(8+C)=3.25(8-C) Isolate C 4.75C = 8(3.25-1.5) C=8*1.75/4...
*June 19, 2013*

**maths - question incomplete**

So far, ABC is just any triangle. The addition of the altitudes do not help. If it is further specified that BD intersects the segment AC at D, and CE intersects segment AB at E, and that BD and CE are equal, then it is possible to prove that triangles EBC and DCB are ...
*June 19, 2013*

**statistics**

A two-tailed test of a=0.05 is equivalent to two tests of a=0.05/2=0.025 for each for the upper and lower tails. So for |z|>1.96 has a=0.025 (two tailed) is equivalent to z>1.96 and z<-1.96. Ref: http://www.math.unb.ca/~knight/utility/NormTble.htm
*June 18, 2013*

**math**

Here m=7.50 / shirt b=set-up fee Since we know that 2450=7.5(300)+b => b=2450-7.50*300 =2450-2250 =200 So y=7.50x+200
*June 18, 2013*

**Math**

All good to me. For number 3, I am not sure if I understand the context of the question. I interpret it to mean what variable can adversely affect the accuracy of extrapolated data, in which case I choose independent variable. If an independent variable is chosen out of the ...
*June 18, 2013*

**maths**

Distance travelled in one revolution = 2 × π × r where r is 3 cm. Distance travelled in 15 revolutions will be 15 time the above amount.
*June 18, 2013*

**computer science**

Read some of the articles on the subject, post a rough draft of your description, and we will be glad to critique your work. Some possible articles could be: http://en.wikipedia.org/wiki/Programming_language http://en.wikipedia.org/wiki/Category:Computer_languages
*June 18, 2013*

**Math**

FV=PV*(1+i)^n i=interest per period (year) expressed in fraction, =0.05 in this case. n=number of periods (year), = 12 in this case Your calculator can now be put to good use. Post for an answer check if necessary.
*June 17, 2013*

**Math**

We need to know how often interest is accrued. It is not always equal to the payment frequency. Some banks compound every 3 months, some six months, and some a year. For lack of information, we will assume that interest is compounded monthly, which simplifies the calculations...
*June 17, 2013*

**algebra**

Distance driven = 50 mph * (1/2) hour = 25 miles Distance to go = 100-25=75 miles.
*June 17, 2013*

**Physics**

acceleration =(v1-v0)/t =(34-10)/5.35 m/s² =4.486 m/s²
*June 17, 2013*

**math**

See http://www.jiskha.com/display.cgi?id=1371989906
*June 17, 2013*

**maths**

y2:x2=y1:x1 so y2=(y1/x1)*x2 =(15/9)*33
*June 17, 2013*

**math**

Height=Horiz. distance * tan(∠elev) =42*tan(36°)
*June 17, 2013*

**mathematics**

The way to proceed is: 1. plot the two points (3,-7) and (-9,21) on graph paper 2. join the two points with a straight line (using a straight-edge) 3. If the line passes through the origin, then the two ratios are in proportion.
*June 17, 2013*

**Algebra 2 ..**

(-16)^(1/4) =((-16)^(1/2))^(1/2) using rules of exponents =√√(-16) =√(4i) =√(2²i) =2√(i)
*June 16, 2013*

**algebra**

If you compare two graphs, which we don't see, you will need to describe or define the axes of the graphs. Does the x-axis represent the amount of gas consumed in gallons, and the y-axis represent the distance travelled? If that is the case, the rate of change represents ...
*June 16, 2013*

**Programming**

If you need debug help, please 1. specify the compiler/language 2. supply error messages you got when the programme was executed or compiled. 3. indicate if it is a compilation, execution or logical error. This one looks fishy: output "Enter student name or ", QUIT...
*June 16, 2013*

**math**

Choosing 3 out of 11 is given by: 11C3 =11!/[(11-3)!3!] =11*10*9/(1*2*3) =165
*June 15, 2013*

**math trigonometry**

See: http://www.jiskha.com/display.cgi?id=1371300101
*June 15, 2013*

**st.paul**

112,000,000,000
*June 15, 2013*

**mATHS**

Take away the legs of the 3 extra stools, which leaves us with 72-9=63 legs for equal number of stools and tables. Divide 63 by the total number of legs of one of one set (7 legs for 1 table and 1 stool), we have 63/7=9 sets. So he made 9 tables and 12 stools.
*June 15, 2013*

**trig**

Since (5,12,13) is a Pythagorean triplet, tan(θ)=5/12. Mathematically, we solve it by: Divide by the right hand side: (5/13)sin(θ)+(12/13)cos(θ)=1 Since (5/13)²+(12/13)²=1, we can put 5/13=sin(φ) 12/13=cos(φ) so sin(φ)sin(θ)+cos(&...
*June 15, 2013*

**maths**

common ratio = (1458/2)^(8-2)= ±3 So the g.p.s are 2/3,2,6,18,54,162,486,1458 or -2/3,2,-6, ....1458
*June 15, 2013*

**physics**

Acceleration phase: initial velocity, v0 = 0 m/s final velocity, v1 = at = 8*20 = 160 m/s distance, S = ut+(1/2)at² = 0 + (1/2)8(20²) =(1/2)8(400)=1600 m Free fall phase: v0 = 160 m/s acceleration,a = -9.8 m/s² v0 = 160 m/s v1 = 0 a = g =-9.8 m/s² use v1&...
*June 15, 2013*

**math**

I guess I did not interpret the question correctly the first time around. "At least 4 blocks" means that the 2nd, 3rd, 4th streets (north-south) are not accessible. Similarly, the 2nd to the 12th avenues (east-west) are not accessible. So near the starting point ...
*June 15, 2013*

**math**

All of them. Since there are 46x46 streets, there are 45x45 blocks. The dog has to run 4 blocks in a row in the horizontal direction, and 12 blocks in a row in the vertical direction, both of which are even numbers, it will never reach the food, in which direction it tries.
*June 15, 2013*

**Calculus**

f(x)=ax²+bx+c f'(x)=2ax+b f"(x)=2a f"(2)=3 => 2a=3 => a=3/2 f'(2)=2 => 2a(2)+b=2 => 3(2)+b=2 => b=-4 f(2)=6 => a(2)²+b(2)+c=6 => 4a+2b+c=6 => 6-8+c=6 => c=8 Therefore f(x)=(3/2)x²-4x+8 Using this final definition of f...
*June 14, 2013*

**maths**

Does an operation between two members of a group give you a unique value or multiple values?
*June 14, 2013*

**math**

When a problem requires "at least one", it is often easier to find the probability of getting none and subtracting the probability from 1 (complement). Here, probability of not getting a king at a draw is 48/52, or 12/13. Probability of getting no king at 4 ...
*June 14, 2013*

**Calculus**

f(x)=x+4/x f'(x)=1-4/x^2 f'(2)=1-1=0 Equation of tangent line: y=0(x-2)+4, or y=4
*June 12, 2013*

**Geometru**

A heptagon has 7 sides. The sum of exterior angles is 360. The six given angles have exterior angles equal to: 60,30,45,10,90 and 55 for a total of 290. The remaining exterior angle is therefore 360-290=70°. The largest exterior angle is 90°.
*June 12, 2013*

**algebra**

For √, type in & r a d i c ; but without the intervening spaces. I will solve the first one: Use the FOIL rule (2√5-√28)(√28+4√5) =(2√5-2√7)(2√7+4√5) =4(√5-√7)(√7+2√5) =4(10-7-√5√7) =12-4...
*June 12, 2013*

**math check**

Sorry, the second one is P(z<1.51), which makes 0.9354 the correct answer.
*June 11, 2013*

**math check**

Four decimal places for 0.409 should be 0.4090. The second one is correct.
*June 11, 2013*

**math**

These two lines are parallel and distinct, hence there are no solutions. Show that this is the case by dividing the first one by two to get 5x+5y=515 Since both equations have 5x+5y on the left, and different values on the right, it shows that the two lines are parallel and ...
*June 11, 2013*

**math**

What do you think, and why?
*June 11, 2013*

**math**

P=principal = $3000 i=interest=0.06 n=number of 6-month periods FV=future value =P(1+i/2)^(n)
*June 11, 2013*

**ssm**

acceleration = v²/r
*June 11, 2013*

**math**

The probability of a red pen on the first draw is 4/18. For the second draw, there are 3 red pens left out of 17 pens total. The probability of both happening is obtained by multiplying the two probabilities: P(RR)=(4/18)*(3/17)=2/51
*June 11, 2013*

**math**

There are 2^10 possible subsets, including Φ, the null set. Not sure what you mean by sum of the elements, do you mean the sum of the cardinalities of the 1024 subsets, or do you mean the sum of the numbers of each subset? In the case of the latter, the distinct sums would...
*June 11, 2013*

**math problem**

Assume that the "grid" means "grid of squares" is the collection of all the squares, then we consider one square: The "safe" area for the centre of the coin is a square of 1/2"x1/2" out of a total of 1.5"x1.5". Probability is ...
*June 11, 2013*

**math**

Rewrite the word as: "ceeeffitv" we see that it is a 9 letter word in which the letters e and f repeat 3 and 2 times respectively. The number of permutations is therefore 9!/(3!2!1!1!1!1!) =30240
*June 11, 2013*

**math**

Since "education" can be written as "acdeinotu" a nine letter word without repetition, the number of permutations is 9! = 362880
*June 11, 2013*

**computer**

There are many free C/C++ compilers available. Notable ones could be Microsoft's Visual Express C++, Dev-C, Borland C/C++ compilers. Cnet has a whole section for that purpose. Note that some of the compilers listed at the Cnet site are try and buy. Here are some links: ...
*June 11, 2013*

**Probability**

P(odd)=0.75 P(even)=0.25 P(3)=0.75/3=1/4 P(6)=0.25/3=1/12 Since 3 and 6 are mutually exclusive, P(3∪6)=P(3)+P(6)=1/4 + 1/12 = 1/3
*June 10, 2013*

**Geometry**

The radius is the distance between the centre and the given point, which is r=sqrt(15^2+4^2)=sqrt(241) The circle with centre (2,-5) is (x-2)^2+(y-(-5))^2=r^2 There is only one choice that fits these criteria.
*June 10, 2013*

**Number Theory**

Yes, it works! If we solve a,b,c in terms of d, we get, a=-(d+36)/6, b=d+11, c=-(11d-24)/6 from which we can define f(x)=x^4 -(d+36)x^3/6 +(d+11)x^2 -(11d-24)x/6 +d and based on this, f(1)=10 f(2)=20 f(3)=30 f(12)+f(-8)-19000 =-608(d+36)/3 +208(d+11)+2d+2(24-11*d)/3 +5832 =840
*June 10, 2013*

**Geometry**

It is a conditional probability problem where the distribution is binomial. The general expression for conditional probability for probability of event A given event B is P(A|B)=P(A∩B)/P(B) where A = P(exactly 2 heads) B=P(at least one head) P(A∩B)=P(A) since A is a ...
*June 10, 2013*

**Algebra**

If the length and width of the pool are L and W, and the width of the path is w, then perimeter of the pool = 2(W+L) perimeter of the outside = 2(W+2w + L+2w) Difference between outside perimeter and the pool =2(W+2w + L+2w) - 2(W+L) =8w So w=(74-50)/8=24/8=3 m
*June 10, 2013*

**maths**

Use FOIL to expand (x+1)(x+2) =x²+2x+x+2 =x²+3x+2
*June 10, 2013*

**maths**

Does (x+1)3 stand for (x+1)³ or 3(x+1) ?
*June 10, 2013*

**maths**

(x+1)3=2f(x+1) Transpose the two, and switch sides f(x+1)=(x+1)³/2 Since x+1 is the argument of the function, we replace y=x+1 and express the right-hand side in terms of y: f(y)=y³/2 Therefore: f(10)=10³/2
*June 10, 2013*

**Hello? My math question was ignored?**

See http://www.jiskha.com/display.cgi?id=1370816233
*June 9, 2013*

**Math**

(x+2)(x+1)=x²+3x+2 Multiply by 9: 9x²+27x+18 Now put it all together: 9x²+27x+18 -2x-2 -4x-4 = 0 group like terms: 9x²+21x+10=0 The next step is to factorize the expression by grouping: Find m, n such that m+n=21, m*n=90 so m=6, n=15 9x²+6x +15x+10 = 0 ...
*June 9, 2013*

**Algebra II**

There are infinitely many of them. Are you given a list of choices?
*June 9, 2013*

**Math**

Let ω=angular velocity (rad/s) To offset gravity, the centripetal force must offset gravity, g, or rω²=g Solve for ω.
*June 9, 2013*

**French**

The difference between the two sentences is the adjective "vert", which varies according to gender and number vert (masc. sing.) verte (fem. sing.) verts (masc. plur.) vertes (fem. plur.) Since herbe is a feminine noun in singular, you will choose the adjective , and...
*June 7, 2013*

**Math check and question**

What did you do for #a? P(n=1, x=0, p=0.15) =nPx 0.15^0((1-0.15)^(1-0) =1!/(0!1!)(0.15^0)(0.85)^1 =1*1*0.85 =0.85 For #b, P(n=3,x=3,p=0.15) =3P3 (0.15^3)(1-0.15)^(3-3) =1*(0.003375)(0.85^0) =0.003375 Check out the other numbers using P(n,x,p) =nPx (p^x)(q^(n-x)) where q=(1-p)
*June 6, 2013*

**Algebra**

Solve the equation -16t^2+20t+6 = 0 will give you the times that the ball is on the ground. The negative root accounts for the fact that the ball is 6 feet above ground at t=0. I get t=3/2 and t=-1/4
*June 6, 2013*

**C++**

C++ is just another programming language. If you have already programmmed in other languages, switching to C++ will not be difficult. On the other hand, if you are programming for the first time, you will be learning two things at the same time: programming concepts, and the C...
*June 6, 2013*

**Calculus**

Volume of pyramid =area of base * height /3 For a square base of side s, Volume =(s²h)/3
*June 5, 2013*

**Calculus**

e^x is non-negative, so the volume is the definite integral from 0 to 10 of I=∫A(x)dx =0.01*10e^0.01x =0.1*e^0.01x evaluated from 0 to 10
*June 5, 2013*

**maths**

f(208)=208/207+208/207×206/205+208/207×206/205×204/203+… =208 This can be obtained by induction: Let f(n) be the function such that: f(n)=n/(n-1) + n/(n-1)*(n-2)/(n-3) + … n/(n-1)*(n-2)/(n-3)…(2/1) where n is even. Then f(2)=2/1=2 f(4)=4/3+(4/3...
*June 5, 2013*

**maths**

Do you agree with the following response? http://www.jiskha.com/display.cgi?id=1370323034
*June 5, 2013*

**probability statistics**

Assume population height follows a normal distribution N(μ,σ), then the top 4% falls above μ+1.75σ (approximately) as read from the normal distribution table.
*June 4, 2013*

**Math**

3/5-2/5=1/5 So proportion is 1/5 of the class equals 12 students So the whole class is 5*12=60 students. # of Girls = 60*2/5=24
*June 4, 2013*

**math**

Volume = 256 m³ Let base = x by x m height = 256/x² Surface area = x²+4(x)(256/x²) =x²+1024/x differentiate with respect to x and equate to zero for extremum: 2x-1024/x²=0 x=8 So the box size is 8x8x4 high Note: I have assumed that the base area ...
*June 4, 2013*

**algebra1**

Remove the first set of parentheses with no change of the contents. Remove the second set of parentheses but change the sign of each term in the parentheses, since the parentheses are preceded by a negative sign. (3x^2-2x-1)-(5x^2-4x-2) =3x^2-2x-1-5x^2+4x+2 Now group like ...
*June 4, 2013*

**math 7**

experimental probability = (no. of successes) / (total number of trials) =8/20 =2/5
*June 4, 2013*

**comptuer programming**

There are quite a few things to note. I believe your hour rate is multiplied by 1.5 only for those hours exceeding 40 hours. The way you're doing it, it will never get changed because the hour rate is changed AFTER you calculated the total. Don't know what you want to ...
*June 4, 2013*

**maths - typo**

Please check you post. I think 4.2 m is not the right length because if you add any two sides of a triangle, it should be greater than the third side. Here 4.2+(hypotenuse-14)=hypotenuse-9.8 which is shorter than the hypotenuse. It probably reads 42. Let x=length of the other ...
*June 4, 2013*

**Maths**

I have a winning strategy, but perhaps there are others. Draw a line of symmetry to split the game into two identical games. Whatever the next player does, you would do the mirror image. Therefore you will end-up splitting the last rectangle. Based on this, there are only two ...
*June 4, 2013*

**Math**

Let O = centre of circle Γ, then ∠PAO=90° Consider ΔPAC, use sine rule to find ∠PAC, which equals 13° (approx.). ∠CAO is therefore 90-∠PAC and equals 77° approx. Since Δ CAO is isosceles, with congruent legs equal to the radius r ...
*June 4, 2013*

**Math**

Let O = centre of circle Γ, then ∠PAO=90°
*June 4, 2013*

**Math**

I have one feasible solution, not sure if it is optimal. You can find others for a check along the same lines. C=4, 3 factors: 1,2,4 B=6, 4 factors: 1,2,3,6 A=12,6 factors: 1,2,3,4,6,12 N=72,12 factors: 1,2,3,4,6,8,9,12,18,24,36,72
*June 4, 2013*

**Math**

brake. Use the kinematics equation v2²-v1²=2aS v2=final velocity v1=initial velocity S=distance travelled a=uniform acceleration. I get approximately 20 m/s if I assume you mean deceleration of 4.5m/s or acceleration of -4.5 m/s. Deceleration of -4.5 m/s will ...
*June 3, 2013*

**Velocity**

v^2 = 11m/s + 2 * 9.81m/s^2 * 60 should read: v =sqrt( 11m/s ² + 2 * 9.81m/s^2 * 60 ) I get about 36 m/s
*June 3, 2013*

**math**

x=Bessy y=Bob x=6y (Bessy has 6 times as much as Bob) x+6=3(y+6) (when each earns $6, Bessy will have 3 times as much money as Bob) Solve for x and y
*June 3, 2013*

**math**

The only right triangle that I know of which has the side lengths form an arithmetic sequence is (3,4,5) or multiples thereof. If the 8 cm leg is the shortest side, then we can find the remaining sides by proportions, namely 8 cm, 8*4/3=32/3, 8*5/3 = 40/3 If the 8 cm side is ...
*June 3, 2013*

**Math**

A=cost of adult ticket C=cost of child ticket 9A+2C = 252 A=C+6 Use substitution 9(C+6)+2C = 252 9C+2C = 252-54 11C = 198 C=18 A=C+6=24 Check: 9A+2C=9*24+2*18=216+36=252 OK
*June 3, 2013*

**pcm**

I assume you mean what is the minimum possible value of f(75p²). Is it known if p is greater than 5? If it is, would it be the number of distinct factors of 75 multiplied by 3 (6*3)=18, namely 1,3,5,15,25,75, then multiply each one by p, and then multiply each one by p&...
*June 3, 2013*

**tech III math ( ACT Prep)**

You need the LCM (lowest common multiple) of the two numbers. Here's a systematic way to find the LCM between two numbers. In the following calculation, the number on the right is a common factor. Extract a common factor on each line (write on the right). Then divide each ...
*June 3, 2013*

**Statistics**

Binomial distribution, n=10 p=0.28 q=1-0.28=0.72 mean=np variance=npq std dev=sqrt(npq) Exactly r successes =P(r) =nCr p^r q^(n-r) Work out each of the above problems and you will find a match. For example, the first one: P(no more than 3 tails) =P(0)+P(1)+P(2)+P(3) =0.037+0....
*June 2, 2013*

**To Sarah: please do not multiple post the same question **

Sorry for having misspelled your name.
*June 2, 2013*

**To Sara: please do not multiple post the same question**

There are people on earth who work with 56kb Internet connections, which means that the 3 seconds that you take to make each of the quintuple posts, it could take up to 3-4 minutes for others to just to display it. The Air America problem is a multi-step experiment, where ...
*June 2, 2013*

**algebra**

xy=36 x+y=26/2=13 Since 4*9=36 and 4+9=13 we have the sides of the rectangle as 4 and 9 yards.
*June 2, 2013*

**algebra 2**

Use the given formula i=500 mg r=(1-0.25)=0.75 (fraction of what remains) t=6 hours e=base of natural log a(t)=amount left after t hours in mg. a(t)=i e^(rt)
*June 2, 2013*

**algebra**

By proportion, you get 2.5%-1%=1.5 1%-0.25%=0.75 Ratio=1.5:0.75=2:1 To make the mixture, we use the inverse of the ratio, therefore Mixture=1:2, or 120g of 2.5% and 240g of 0.25% make 360g of 1% (assuming both have same density). Check: (120*.025+240*.0025)/360=1% You can also...
*June 2, 2013*

**physics**

Hint: Calculate the time it takes to reach the lower roof, say t (in seconds), by solving for t in: (100-25)=(1/2)gt² The minimum horizontal velocity will be 20/t m/s
*June 2, 2013*

**Math check**

Check your calculations! Did you get standard deviation or σ² as 2.88? Don't understand how you got 2.88 and 10.58. Can you post what you did? For the variance, I have 1.49+0.09+0.00+0.14+1.39=3.1
*June 2, 2013*

**Math check**

First step: Check to see if it is a discrete probability distribution by summing all probabilities. If it does not equal one, either the given distribution is incomplete, or it is not a discrete distribution. Second step: Mean (expected value of X, E(X), μ) =ΣX*P(X) =...
*June 2, 2013*

**statistics**

Let D=event that a television selected is defective and ~D=event that a television selected is NOT defective Then probability that both are not defective: P(~D~D)=(5/9)(4/8)=5/18 Therefore at least one defective is its complement P( (~D~D)') = 1-5/18 = 13/18
*June 2, 2013*

**Math**

Follow the same strategy as the previous problem, we make use of given information and deduce values by expansion. Let f(x)=x^2+(a+6i)x+b+12i=0 and given that f(x) has a repeated root, we deduce that the discriminant is zero, i.e. (a+6i)²-48i=0 which expands to a²-4b...
*June 2, 2013*

**Math**

Let z=a+bi where i²=-1 then z²-26z =-b²-26a + (2a-26)bi Since is real, and z is non-real, therefore b≠0, and consequently (2a-26)bi = 0 => 2a-26=0, => a=13 Thus z=13+bi, z(conjugate) = 13-bi so z+z(conjugate)=13+bi+13-bi=26
*June 2, 2013*

**Math**

Overall loss, neglecting benefit from use of the car, is loss = $20,000 - $18,200 = $1800 It is a loss because he ended up with less money than the start.
*June 2, 2013*

**Calculus**

Define the surface as: f(x,y,z)=xy^2+zy^2+4y-xz^2-18=0 Then check that P0(-2,0,3) is on the surface by evaluating f(-2,0,3) and confirm that it is zero. Let fx,fy,fz be the partial derivatives of f(x,y,z) with respect to x,y and z respectively, and evaluated at P0(-2,0,3). The...
*June 2, 2013*

**math check**

Your answer corresponds to P(-0.25<z<0). Look up a probability table (or use your calculator) for +1.32. Many normal probability tables are one-tail from -∞ so you need to subtract 0.5 from the result, taking advantage of symmetry of the normal distribution.
*June 2, 2013*

**check math**

Correct!
*June 2, 2013*

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