Sunday
January 25, 2015

Posts by MathMate


Total # Posts: 10,888

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

statistics
Normally distributed data are symmetric about the mean, so 50% goes above and the other 50% goes below the mean.
May 26, 2013

statistics
By definition: P(B|A)=P(B∩A)/P(A) So 0.4=P(B∩A)/0.5 Solve for P(B∩A)
May 26, 2013

statistics
1.0 When data fit exactly onto a straight line, the correlation coefficient is either +1 or -1. If the slope of the line is positive, r=+1. If the slope of the line is negative, r=-1. In this case, the slope=+2, so r=+1.0
May 26, 2013

Math
Zero. g(x) is the tangent to f(x) at x=-3. Show that this is the case by solving for x in the equation f(x)=g(x) and show that it has a double root.
May 26, 2013

French
Conjugaison du verbe "avoir" (to have) au présent indicatif: j'ai tu as il a nous avons vous avez ils ont Since your subject is "je", or I, first person singular, we need to use "ai". "as" is for second person singular. Also, ...
May 26, 2013

math
45-45-90 triangle is isosceles. The other short side is therefore also x. Using Pythagoras theorem, we find hypotenuse²=x²+x²=2x² Solve for hypotenuse.
May 26, 2013

coefficients
A coefficient is the numerical part of each term. 5x^2+3x+66 has coefficients 5, 3, and 66 for the first, second and third terms respectively.
May 26, 2013

Polymonimals!
When you have a negative sign preceding parentheses, do an extra step to remove the parentheses: (m^2-m-4)+(m-5) =m^2-m-4+m-5 =m^2-m+m-4-5 =m^2-9
May 26, 2013

vectors problem!!!! help!!!! :)
You're welcome!
May 26, 2013

vectors problem!!!! help!!!!
This is the magnitude of the cross product. The cross product is obtained by evaluating the determinant p i j k 2 9 0 13 18 0 which is p=0i+0j+(2*18-9*13)k =-81k The magnitude is therefore 81.
May 26, 2013

Statistics
I think you have the right formulas, but the wrong N. N equals 5 (count either number of x values or number of y values). So SSx=197-31²/5=4.8 SSy=39000-440²/5=280 Sxy=2760-31*440/5=32 r=Sxy/sqrt(SSx*SSy)=0.87287
May 26, 2013

Statistics
I was questioning SS(xy) only. We need Sum of xy for calculating other parameters, but not sum of squares of xy. How did you get your answers? I got 197 for SS(x). All of your answers seem to come up a little more than half of mine.
May 26, 2013

Statistics
I do not know if we use the same terminology. Is SS(x) sum of squares of x? If it is, I get 197. Would it be S(xy) instead of SS(xy), meaning just the sum of the products? Does r mean coefficient of correlation, which has a range of -1 to 1. If you get 7.04, perhaps you are ...
May 26, 2013

help!!!!! Probability!!!::)
You're welcome! It would be even better if you would not use various aliases.
May 26, 2013

help!!!!! Probability!!!
Assume die is fair. Rolling twice gives 36 outcomes, of which the second roll is strictly less than the first (successes) can be enumerated as follows: 21,31,32,41,42,43,51,52,53,54,61,62,63,64,65 Count how many successes there are, and divide by the size of the sample space (...
May 26, 2013

math
There is not much to simplify. Is the integration from a to b or from b to a? Your answer is close, but has the wrong sign and missing a term. Remember that e^0 is 1 and not zero.
May 26, 2013

integral calculus
You may want to show your work to know how you got your answer. The good news is that your indefinite integral is correct, but off by 1/24, which can be absorbed in the integration constant. Depending on how you integrated, it could give equivalent results of: (3sin(x)^4-2sin(...
May 26, 2013

Engineering science
Hints: Kinetic energy, KE=(1/2)mv² where m=mass of object (kg) v=velocity (m/s) Potential energy =mgh m=mass in kg g=acceleration due to gravity, m/s-2 h=height above datum in m. To calculate h, you need the distance travelled. For uniform acceleration, distance d, is the...
May 26, 2013

math
The question gives the length of the original log as 50 cm (unless there is a typo). If the two pieces are equal, then each piece would measure 50/2 cm = 25 cm.
May 26, 2013

Statistics
Maple can certainly find r, called the coefficient of correlation. The coefficient of correlation, r, for a population can be calculated using the following formula (one of the different forms): r=(nΣxy-(Σx)( Σy)) / √[(nΣx²-(Σx)²)(...
May 26, 2013

Statistics
Are you expected to use Maple to do this exercise? What are the answers?
May 26, 2013

math
According to the question, 5.13 is in tens of thousand of dollars, so the correct answer should be $51300, and the $ sign is already given before the answer box, right?
May 26, 2013

math
"y (in tens of thousands of dollars)"
May 26, 2013

physics
Acceleration of an object in circular motion is: magnitude = v²/r v = 2 m/s r = 0.5 m Direction is towards the centre of the circle. Mass is irrelevant (unless you need the force on the string).
May 26, 2013

math
Since the fraction of boys who play the games cannot exceed 1, so 4/7+5/8-1 is the fraction who plays both games. 5/8+4/7 - 1 =(35+32-56)/56 =(67-56)/56=11/56
May 26, 2013

French
Bravo, c'est une production écrite créée avec soin! A few little things: - "à Dubai mall" : do you mean a shopping centre? (centre commercial) unless it is a proper name, in which case you would write "Dubai Mall". - "...
May 26, 2013

Math
Let's say we each have two apples. If I give you one apple, you have three and I have one. So the difference is 2 apples. If I give you two apples, you have four and I have none, the difference is 4. We conclude therefore that for every apple I give you, the difference ...
May 26, 2013

Math (Absolute Value Inequality)
You probably would like to find the value of a. We established that to satisfy the quadratic inequality x^2−11x−210 < 0 -10<x<21 Now substitute this interval into each of the two linear inequalities: x-8<a and 8-x <a (-10)-8<a => a>-18 8-(-...
May 26, 2013

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