Search found 92 matches


Total number of ways of choosing 2 balls is 8C2 = 8!/6!2! = 28 Prob of picking a white ball first time = 3/8 Prob of picking a white ball second time (having not picked it first time) = 5/8 * 3/7 = 15/56 Total prob of picking at least one white ball = 3/8 + 15/56 = (21+15)/56 = 36/56 = 18/28 Number ...

by moutar

Wed Apr 22, 2009 11:15 am
Forum: Problem Solving
Topic: Another Permutation
Replies: 3
Views: 891

I differentiated to check. Obviously it can be done by logic. I'll write both. Differentiating: Max when dP/dS = 0 dP/dS = 2(S-4) (by the chain rule) 2(S-4) = 0 when S = 4 Logic: As it says (S-4)^2 is always positive (or 0). So -2(S-4)^2 is always negative and will take passengers away from the 32. ...

by moutar

Wed Apr 22, 2009 10:58 am
Forum: Problem Solving
Topic: MGMAT cat 6B PS
Replies: 2
Views: 714

Let the perfect square be denoted: S=a^x+b^y+c^z. x y and z must all be even for S to be a perfect square. Possible values of x are 0, 2, 4 (Total 3) Possible values of y are 0, 2 (Total 2) Possible values of z are 0, 2, 4, 6 (total 4) So total possible factors = 3*2*4 = 24 I actually disagree with ...

by moutar

Wed Apr 22, 2009 10:45 am
Forum: Problem Solving
Topic: a, b, c > 2
Replies: 6
Views: 1147

Choose values of x and y such that 3x + 7y is a multiple of 11. x = 5, y = 1 works Plug each of these into the answers and you'll find that: 1. 4x + 6y = 20 + 6 = 26 WRONG 2. x + y + 4 = 5 + 1 + 4 = 10 WRONG 3. 9x + 4y = 45 + 4 = 49 WRONG 4. 4x - 9y = 20 - 9 = 11 5. 7x + 4y = 35 + 4 = 39 WRONG There...

by moutar

Mon Apr 20, 2009 11:05 am
Forum: Problem Solving
Topic: multiple
Replies: 5
Views: 1042

a + b + c = 100

As said above one of the prime number needs to be 2.

2 + b + c = 100

b + c = 98 ... (1)

We know the difference between b and c is 36.

c - b = 36 ... (2)


(1) - (2) ... 2b = 62 => b = 31

c = 36 + 31 = 67 - Answer: 5

by moutar

Mon Apr 20, 2009 10:48 am
Forum: Problem Solving
Topic: prime
Replies: 3
Views: 842

There are 9 different combinations that can happen. Take Jim as the first one and Renee the second.

RR RP RS
PR PP PS
SR SP SS

The combinations RS, PR and SP will give Jim a win so the probability of him winning is 1/3. E.

by moutar

Sun Apr 19, 2009 5:23 am
Forum: Problem Solving
Topic: rock, paper and scissors
Replies: 3
Views: 980

I would completely agree with you there.

by moutar

Sat Apr 18, 2009 2:02 am
Forum: Problem Solving
Topic: triangle
Replies: 1
Views: 692

There are 15 other fruits.

Percentage = Difference/Other fruits x 100
= 35-15/15 x 100
= 20/15 x 100
= 133.33%


I don't like the wording of the question. It sort of makes sense but could have been written better. Is this the exact question?

by moutar

Sat Apr 18, 2009 2:01 am
Forum: Problem Solving
Topic: apples
Replies: 2
Views: 937

Let t be the number of tomatoes and p be the number of peppers. From the information given we can form 2 simultaneous equations. .75t + .6p = 30 (1) 4t + p = 116 (2) (1) x 20: 15t + 12p = 600 (3) (2) x 12: 48t + 12p = 1392 (4) (4) - (3): 33t = 792 t = 24 t=24 into (2): 4x24 + p = 116 96 + p = 116 p ...

by moutar

Sat Apr 18, 2009 1:56 am
Forum: Problem Solving
Topic: peppers
Replies: 2
Views: 1049

Let a be the length of the table.

Length of strip: 3 + a + 3 + a = x
6 + 2a = x

Surface area: 3a = x

Equate the x's:

3a = 2a + 6
a = 6

Answer E

by moutar

Mon Apr 13, 2009 6:43 am
Forum: Problem Solving
Topic: Perimeter
Replies: 4
Views: 1638

25% = 1/4

45% = 9/20

Let y be the total sales in the USA.

Then x = y*1/4*9/20
= 9y/80

y = 80x/9 E.

by moutar

Mon Apr 13, 2009 4:48 am
Forum: Problem Solving
Topic: Easy one!
Replies: 1
Views: 1109

Range = biggest - smallest
= 17 - 4
= 13

D.

by moutar

Sun Apr 12, 2009 4:16 pm
Forum: Problem Solving
Topic: range question
Replies: 2
Views: 1170

The whole belt is made up of 2 horizontal parts (top and bottom) and 2 round half-circumference parts.

So:

15 = Top + bottom + 2 x half circle

Top = bottom (call this A)

15 = 2A + 2 x pi*d/2 (d=1)
15 = 2A + pi

15 - pi = 2A

A = (15 - pi)/2

by moutar

Sun Apr 12, 2009 3:44 pm
Forum: Problem Solving
Topic: applied circumference problem..finding distance?
Replies: 4
Views: 999

angle ABC = 90 degrees (angle subtending a diameter) AB^2 + BC^2 = AC^2 AC = 2, BC = 1 -> AB^2 + 1 = 4 AB^2 = 3 AB = root(3) Area of triangle = 1/2 x base x (perpendicular) height = 1/2 x BC x AB = 1/2 x 1 x root(3) = root(3)/2 B.

by moutar

Sun Apr 12, 2009 3:14 pm
Forum: Problem Solving
Topic: inscribed or circumscribed
Replies: 3
Views: 849