Friday

February 27, 2015

February 27, 2015

Total # Posts: 10,916

**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*

**check math**

Your answer corresponds to at least one boy in a family of 6. Retrace what you did and work it out for a family of 8. "At least one boy" corresponds to "NOT all girls". So calculate the probability of having all girls in the family, and subtract from 1.0 to...
*June 1, 2013*

**math**

Sale price = normal price *(1-markdown) =$2.77(1-0.22)=$2.16 It must have been a while back since Macy's sold a designer jacket for $2.77.
*June 1, 2013*

**Math check my answer**

Since we are talking about costs, a better deal is a lower cost, so the inequality should read: .80x + 29 < 1.19x + 17 The answer is almost perfect... 30.769 rounds to 30.8, although in this case, it does not count because we are talking about integers.
*June 1, 2013*

**math**

Work with the "weighted mean". For each pound, cost of meat powder = 0.4*1.20 = 0.48 cost of grain = 0.6*0.80 = 0.48 Total cost per pound = 0.48+0.48 = $0.96
*June 1, 2013*

**programming**

What have you done so far, and how would you like us to help? Can you show us your pseudocode?
*June 1, 2013*

**arithmetic**

Set up a table of outcomes and the corresponding probabilities to create the probability distribution. For example, the lowest outcome is X=2 (=1+1) with probability 1/36. then X=3 (1+2 or 2+1) with probability 2/36 ... X=12 (=6+6) with probability 1/36. Find the mean using E(...
*June 1, 2013*

**arithmetic**

Did you read your other post? http://www.jiskha.com/display.cgi?id=1370132243 Set up a table of outcomes and the corresponding probabilities to create the probability distribution. For example, the lowest outcome is X=2 (=1+1) with probability 1/36. then X=3 (1+2 or 2+1) with ...
*June 1, 2013*

**probability**

Create the probability distribution for the random variable X (see other post), and sum probabilities of all outcomes greater than 7.
*June 1, 2013*

**Math**

For 23)(ii) I have σ=√(npq)=√(379*0.15*0.85)=6.95 For 24(ii) p=0.89, q=1-0.89=0.11 σ=√(npq)
*June 1, 2013*

**Math**

17% are left-handed means P(left-handed)=0.17 (remember 17%=17/100=0.17) so N=59, p=0.17, q=1-0.17=0.83 you can take it from here!
*June 1, 2013*

**Math**

For a binomial distribution with N bernoulli trials with probability of success p (i.e. failure q = 1-p), the following properties can be proved: mean = Np variance = Npq Take the square-root of variance to get standard deviation. In 15 tosses of a fair dime, N=15, p=0.5, q=1-...
*June 1, 2013*

**math answer check**

I don't know to which question 0.0675 referred. Note that: nCr = n!/[(n-r)!(r!)] For (e), we have P(n=3,x=1,p=0.45) =3C1*0.45^1*(1-0.45)^(3-1) =3*0.45*0.55^2 =0.408375 (f) probabilities never exceed 1! P(n=6,x=6,p=0.25) =6C6*0.25^6*(1-0.25)^(6-6) =1*0.25^6 =0.000244
*June 1, 2013*

**math answer check**

For a binomial distribution, the outcomes are either 1 (success) or zero (failure). The probability of success (outcome =1)of EACH step (out of n steps) is p and remains unchanged over the duration of the experiment. The probability of failure (outcome =0) of EACH step (out of...
*June 1, 2013*

**Math**

Hint: cot^2(x)=cos^2(x)/sin^2(x) =(1-sin^2(x))/sin^2(x) =1/sin^2(x) - 1 cos(x)dx = d(sin(x)) so use the substitution u=sin(x), then du=cos(x)dx cot^2(x) cos(x)dx =(1/u^2 -1)du =(-1/u - u) + C backsubstitute u=sin(x) I=-1/sin(x)-sin(x)+C
*June 1, 2013*

**math-probaility**

Use complementarity. Calculate the probability of getting no lemon, and subtract from 1. Two-step experiment, second step dependent on the first: Total number of candies at start=5 Step 1: Number of grapes=2 Probability(No lemon)= 2/5 Step 2: Number of candies left=4 Number of...
*June 1, 2013*

**Probability**

Expectation = ΣxP(x) where x represents the gain from each of the outcomes in the sample space. Here the gains and probabilities are: outcome=oil gain=375000-25000=350000 P(oil)=1/40 xP(oil)=8750 outcome:gas gain=130000-25000=105000 P(gas)=1/20 xP(gas)=5250 outcome:...
*June 1, 2013*

**Algebra**

Hint:Use the compound interest formula Future=present*(1+i)^n Here Future=40000 n=30 i=0.06 (6%) Solve for Present.
*June 1, 2013*

**heeeeeeeeeeeeelp math**

You were quite right, Andrew. The answer should have been (4!)^4/(4!)² 4! is the number of ways to assemble a single body part. Since there are 4 body parts to assemble, we have (4!)^4 ways to assemble the 4 people where order counts. Since there are 4! permutations of ...
*June 1, 2013*

**Algebra**

There is a rule for this class of problems of finding proportions of mixtures. Most of the time this can be done mentally, for example by chemists or nurses. We have one ingredient A at 20%, and B at 60%. The required mixture is 30% (must be between those of A & B). Take the ...
*June 1, 2013*

**math**

There has been quite a few problems solved on markup based on selling price. This should give you (or others) another example to work on your other problems. retail price = selling price. If there is a 55% markup based on selling price, then the cost price is 100-55=45% So the...
*May 31, 2013*

**Algebra 1**

1. Use the distance formula: distance = (4-1)²+(a-1)²=5² Solve for a (a quadratic equation) 2. Use Pythagorean formula: 8²+b²=14² Solve for b. 3(a) 7²+9²=49+81 = 130 ≠ 12² Therefore the three sides do not form a right triangle. ...
*May 31, 2013*

**Math :)**

You're welcome!
*May 31, 2013*

**Math**

This is a discrete probability function which has the following characteristics: 1. The function is non-negative throughout its domain. 2. ΣR(i)=1 for i∈ domain From the given data, R(0)=0.2 R(1)=0.2 ... R(4)=0.2 for a sum of 1.0.
*May 31, 2013*

**Geometry**

The largest area a given perimeter can enclose is a circle. The largest area of a rectangle for a given perimeter is a square. The question did not specify that the area be a polygon, so the circle gives the largest area. 2πr=18 r=18/2π=9/π Therefore largest area =&pi...
*May 31, 2013*

**math**

Selling price = cost + markup = 47.5 + 34 = $81.50 Mark-up base on cost = mark-up/cost = 34 / 47.5 = 71.6%
*May 31, 2013*

**Math :)**

You're welcome!
*May 31, 2013*

**Math**

Therefore 120 more workers are needed.
*May 31, 2013*

**Math**

Each person accomplishes 1/3÷(60*18) of the project, 1/3240 per person per day. To finish 2/3 of the project in 12 days, Total number of workers need =2/3 ÷ (12*(1/54) =(2/3)*(3240/12) =180 Therefore 120 more workers are needed.
*May 31, 2013*

**maths**

If the original question has a unit of 8m/min., I prefer to give the answer in minutes. The question did not say to answer in hours, and did not say you have to round to the nearest hour. But it is up to you.
*May 31, 2013*

**maths**

Distance travelled =8-(-475) =483 m Speed = 8 m / min. Time = Distance ÷ speed =483÷8 =60.375 minutes
*May 31, 2013*

**Aviation**

See if this link helps answer your question: http://en.wikipedia.org/wiki/Cessna_162_Skycatcher#Specifications
*May 31, 2013*

**Math**

Hints: P(A∪B)=P(A)+P(B)-P(A∩B) If A and B are mutually exclusive (ME), then P(A∩B)=0. This should take care of (d)
*May 30, 2013*

**math**

Nora 4: Hint for you. If you provide attempted answers to the question, do add "(answer check)" to the end of "school subject", especially if you have a whole series of questions which makes it look it homework dumping.
*May 30, 2013*

**math**

Hints: Work out the following: - equal numbers of red marbles and yellow marbles (call x=number of red x=number of yellow - twice as many green marbles as red marbles 2x=number of green Now work out the sample space and the corresponding probabilities.
*May 30, 2013*

**Math**

142=58-7x Add 7x to each side 7x+142=58-7x+7x 7x+142=58 Now subtract 142 from each side to isolate x 7x+142-142=58-142 7x=-84 Divide by 7 to find x 7x/7 = -84/7 x = -12 Now you should be able to try the remaining problems the same way as above and post your answers for checking.
*May 30, 2013*

**Math**

1711 sales out of 1950 calls. The success rate is quite impressive: 1711/1950=87.7%
*May 30, 2013*

**Algebra1study helps**

Multiply both sides by the LCM of the denominators: 3(x+3) to get 1-2*3=2*3(x+3) x+3=(-5)/6 x=-5/6-3 =-23/6
*May 30, 2013*

**algebra**

Let x = number of calculators she can buy, 80x=60*24 x=60*24/80 = 18 Mrs Hopkins can buy 18 calculators at $80 each.
*May 30, 2013*

**math**

39% of selling price is mark-up, so 61% is the cost. Therefore retail selling price =24.30÷0.61 =$39.84 Check: $39.84*0.39=15.54 39.84-15.54=24.3=cost ok.
*May 30, 2013*

**heeeeeeelp math**

Assembling the head, there are 4! ways. Same for each of the three other parts. Total number of ways = 4!4!4!4! But we can arrange the 4 people in 4! different orders, so total number of sets of 4 people = (4!)^4/(4!) =(4!)³
*May 30, 2013*

**Exponential**

Hints: The base is (x^2-17x+71) which does not have rational factors, because 71 has only two factors, 71 and 1, each of which is not a factor to the expression. This means that all integer values of x will make the base non-zero. The exponent, (x^2-34x+240), has two integral ...
*May 30, 2013*

**Maths Please Help - incomplete**

and then...
*May 30, 2013*

**Math/Statistics**

See hints here: http://www.jiskha.com/display.cgi?id=1369881705
*May 29, 2013*

**Math/Statistics**

Hints: P(A∪B)=P(A)+P(B)+P(A∩B) So if any three of the four probabilities are known, we can find the fourth one. Note: Events A and B are mutually exclusive if and only if P(A∩B)=0.
*May 29, 2013*

**Math/Statistics**

(a) P(A|B) conditional probability of A given B =P(A∩B)/P(B) [∩ written as & c a p ; omit the spaces] (b) P(B|A) =P(B∩A)/P(A) (c) A and B are independent if and only if P(A∩B)=P(A)*P(B)
*May 29, 2013*

**Physics**

I assume "linear velocity" means tangential velocity. F=mv²/r =0.25(10²)/3 =25/3 N
*May 29, 2013*

**Math**

#2 is correct.
*May 29, 2013*

**Math**

#2: question incomplete, cannot check. #3: correct You can check: $3*5+$6*6=15+36=$51 #6: correct Check by multiplication 2*5*5*11=550 #7: correct 12-6x2/4+1=12-3+1=10
*May 29, 2013*

**Mathematics**

Assuming "thickness" means height in the usual sense of a cylinder, then volume = πr²h =π(17.1/2)²1.2 =275 cm³ approximately. (π=3.14)
*May 29, 2013*

**math**

See your other post: http://www.jiskha.com/display.cgi?id=1369848822
*May 29, 2013*

**math**

There are 10! ways to place 10 students in 10 chairs in a row. There are 8! ways to arrange a group of 3 students with 7 other students. Among the three students (in a group), they can arrange themselves in 3! different ways. So the probability that they will be seated ...
*May 29, 2013*

**math**

Is the 10 a denominator of the fraction (5-x)/10?
*May 29, 2013*

**math**

Can you please type in the definition of the function exactly as you are given? As it is, it is unclear as to what the function is.
*May 29, 2013*

**math**

What is the domain of the function? P(x)=10 for x=1,2,3,4 and = 5-x otherwise? What is the 10 doing there, please?
*May 29, 2013*

**Maths**

This one has been answered before, just before you stopped posting the remainder. Use intersecting chord properties. The intersection could be inside or outside the circle. AB and CD are chord which intersect at O (inside or outside the circle). Then OA*OB=OC*OD
*May 29, 2013*

**Maths**

If we sum the sequence, S=&sum i, i=1,801, we have S=3²*89*401, as prime factorization. Thus the largest number of groups is 401 sets, each sum would therefore be 801, as follows: {1,800},{2,799}...{399,402},{400,401},{801} for a total of 401 sets.
*May 29, 2013*

**math - discrete math**

We will assume "ways" means order is important, i.e. $5 followed by 5 $1 coins is not the same "way" as 5 $1 coins. We will separate the problem into a few parts. A. No $5 bill $1 bills and coins only, ten of them. Each $1 we have a choice of two ways, coin...
*May 28, 2013*

**Math**

Solve for t in d(t)=25 and d(t)=0, where d(t) is given as: d(t)= -5t^2 + 10t + 20 we find that d(1)=25, and d(3.23)=0. Note: not sure if the diver was on earth. The acceleration due to gravity is only 10 instead of 32.2 f/s2 unless the distance d is in metres.
*May 27, 2013*

**Physics**

Case 1: zero friction F=mg sin(28) a=F/m=g sin(28) S=ut+(1/2)at² 100=0+g sin(28)t²/2 t=sqrt(2*100/(g sin(28)) =6.59 s. Case 2: μk=0.17 Frictional force =μmg cos(28) Net force (assuming μcos<sin) =mg(sin(28)-μcos(28) t=sqrt(2*100/(g (sin(28)-μcos(28...
*May 27, 2013*

**Statistical probability411**

If order is not important 14C7=14!/(7!7!) ! means factorial 7!=7×6×5×4×3×2×1 If order is important, which is not explicit in the question, then the answer is 14P7=14!/7!
*May 27, 2013*

**Statistical probability411**

14C7=14!/(7!7!) ! means factorial 7!=7×6×5×4×3×2×1
*May 27, 2013*

**math**

I think you mean probability is m/n, where m≤n.
*May 27, 2013*

**math**

Perimeter=10, therefore sum of two sides =5. Try sides 2 and 3, area=6, so height=222/6=37. Height=37.
*May 27, 2013*

**algebra probability34**

No replacement (otherwise two identical poems) Total=4+5+2+2=13 poems 5 Colerdge, 2 Byron So P(CB)=(5/13)*(2/12)
*May 26, 2013*

**algebra probabilty34**

14 choose 7 =14C7=14!/(7!7!)
*May 26, 2013*

**math**

The closest point (x0,y0) on the circle to point (x1,y1) of the circle is if (x0,y0) lies on the radial line passing through (x1,y1). To show this, first find the centre of the circle x^2+y^2=1 is a circle with radius 1 and centre (0,0). The line through (0,0) and (3,4) is L...
*May 26, 2013*

**Statistics**

For mean, you add up all numbers and divide by the size of the population. For median, you need to sort them in increasing order, and take the mean of the two middle numbers (average between 25th and 26th values for N=50). Since the data represent the whole population, they ...
*May 26, 2013*

**statistics- correction**

N=10C5=10!/(5!5!)=252
*May 26, 2013*

**statistics**

Assume There are N=10C5 ways of randomly choosing 5 horses out of 10. where N=10!/(5!5!)=25 We assume that 1. order does not count, 2. winning probabilities are equal among horses, 3. results are completely random. Then the owner has one chance in 252 that his 5 horses are ...
*May 26, 2013*

**Math :)**

You're welcome!
*May 26, 2013*

**Math**

April, I see that you have many questions, but have yet to see efforts on your part. I have given a complete solution for this one in the hope that it will help you solve similar problems. If you can show some understanding of the subject matter, such as explaining what ...
*May 26, 2013*

**Math**

Net price factor for 25/15/10 is 0.75*0.85*0.9=0.57375. 0.75 comes from 1-25%, 0.85 comes from 1-15% 0.9 comes from 1-10%. The net price is $800*0.57375=$459
*May 26, 2013*

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