Sunday

December 21, 2014

December 21, 2014

Total # Posts: 10,866

**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*

**Math (Absolute Value Inequality)**

If we would like to satisfy the condition: x^2−11x−210 < 0, we need to find the roots of x^2−11x−210=0. By factoring, we have (x-21)(x+10)=0 The leading coefficient (of x^2) is positive, so the curve is concave up. => x<0 between -10 and 21. To...
*May 26, 2013*

**Math/Algebra**

The ellipse is centred at the origin (0,0). The standard formula for the ellipse is then x²/a²+y²/b²=1 where 2a=distance between vertices on the major axis =(5-(-5)=10, so a=5 Distance between foci 2c=(4-(-4))=8 so c=4 To find b, we use the relation a²...
*May 26, 2013*

**divide radical**

Hint: factorize the numerator: 2b²+2b-6 =2(b²+b-3) which does not have rational factors. You will need to do a division, which is called the Euclidean division (long division), or another method is the synthetic division. It is a little difficult to show the method ...
*May 26, 2013*

**Maths**

Line with slope a through a point (x1,y1) has the equation: y=a(x-x1)+y1 Putting a=-2, (x1,y1)=-1,6), we get the line as: y=-2(x-(-1))+6 or y=-2x+4 ....(1) Substitute x=4 in equation 1 to find the value of y, which is the required unknown.
*May 26, 2013*

**Geometry**

Without knowing the 8 steps to which you are referring, you can do the following: Factor both numerator and denominator: R(x)=(x-5)(x+6)/[(x-5)(x+4)] You will find the zeroes and asymptotes. Since there is a common factor (x-5), the point f(5) is indeterminate and should be ...
*May 25, 2013*

**MATH315 Elementry Statistics**

Some of the requirements of a binomial model are: 1. probability of success is known and does not vary over the experiment 2. Has exactly two outcomes (head/tail, success/failure). 3. has one or multiple steps 4. is a random experiment
*May 25, 2013*

**Math**

Not sure if I understood the question. Does it mean that we need to write the formula A=(B+b)h/2 without using parentheses AND without using the multiplication sign? Would it be: A=Bh/2 + bh/2
*May 25, 2013*

**Math**

Yes, the calculation is correct for the net price factor.
*May 25, 2013*

**math :)**

You're welcome!
*May 25, 2013*

**math**

Hint: a sector is a pie-piece, similar to a slice of pizza. The area of a sector of a given radius is proportional to the central angle. Area of Sector -------------- Area of circle central angle =------------- 360°
*May 25, 2013*

**math :)**

You're welcome!
*May 25, 2013*

**math**

Do it just like normal subtraction, except that when you borrow 1 degree, it becomes 60 minutes, ... 41-20-26 23-39-56 -------- 17-40-30
*May 25, 2013*

**PHYSICS**

Does it come with a diagram?
*May 25, 2013*

**chemistry**

Zn+2HCl -> ZnCl2 + H2 5.5 g of Zn = 5.5/65.382 M =0.0841 M 25 ml of 0.05M HCl = 25/1000*0.05 M = 0.00125 M < 0.0841/2 So the quantity of HCl governs. Assuming all HCl is consumed, amount of Hydrogen = 0.00125/2 M = 0.000625 M Convert that to the required temperature and ...
*May 25, 2013*

**French :)**

Je vous en prie!
*May 25, 2013*

**French**

Give it a try! You must know the name.
*May 25, 2013*

**French**

camping is an English word borrowed by the French language which means 1. the activity of camping 2. camp-ground. "Comment s'appelle" is an expression which translates to "what do you call ...." "ce" => this "terrain de camping"...
*May 25, 2013*

**math :)**

You're welcome!
*May 25, 2013*

**math**

If the length of one of its sides is x. Then x/2 is half the side. An altitude divides the equilateral triangle into two congruent right triangles, each with half of one side (x/2) as the short side, the altitude as the long side, and the side (x) as the hypotenuse. So by ...
*May 25, 2013*

**math :)**

You're welcome!
*May 25, 2013*

**math**

a' ÷ a = b' ÷ b so a' = b' × a / b
*May 25, 2013*

**math :) **

You're welcome!
*May 25, 2013*

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