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probability of the numbers...

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probability of the numbers...

by LevelOne » Sat Jul 04, 2009 3:56 am
Q1

{-10, -6,-5,-4,-2.5,-1,0,2.5,4,6,7,10}

A number is to be selected at random from the set above. What is the probability that the number selected will be a solution of the equation
(x-5)(x+10)(2x-5) = 0?

A. 1/12
B. 1/6
C. 1/4
D. 1/3
E. 1/2

I got three solutions for the equation: 2.5, 10 and -5 but my final answer didn't match with OA. pls explain.

Q2 - you might find them easy

An investment of d dollars at k percent simple annual interest yields $600 interest over a 2-year period. In terms of d, what dollar amount invested at the same rate will yield $2,400 interest over a 3-year period?

A. 2d/3
B. 3d/4
C. 4d/3
D. 3d/2
E. 8d/3

Q3

If the speed of x meters per second is equivalent to the speed of y kilometers per hour, what is y in terms of x?

A. 5x/18
B. 6x/5
C. 18x/5
D. 60x
E. 3,600,000x

thanks
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Re: probability of the numbers...

by rahulg83 » Sat Jul 04, 2009 4:14 am
Q1

{-10, -6,-5,-4,-2.5,-1,0,2.5,4,6,7,10}

A number is to be selected at random from the set above. What is the probability that the number selected will be a solution of the equation
(x-5)(x+10)(2x-5) = 0?

A. 1/12
B. 1/6
C. 1/4
D. 1/3
E. 1/2

I got three solutions for the equation: 2.5, 10 and -5 but my final answer didn't match with OA. pls explain.
Ok, total no of cases = 12C1 = 12
favorable no of cases = 2C1 (because in the set, we have only two solutions, -10 and 2.5)

Ans = 2/12 = 1/6
Q2 - you might find them easy

An investment of d dollars at k percent simple annual interest yields $600 interest over a 2-year period. In terms of d, what dollar amount invested at the same rate will yield $2,400 interest over a 3-year period?

A. 2d/3
B. 3d/4
C. 4d/3
D. 3d/2
E. 8d/3
Interest=P*r*t
Eq 1: 600 = d*k*2
Eq 2: 2400 = x*k*3

Divide them and you ll get x in terms of d..8d/3
Q3

If the speed of x meters per second is equivalent to the speed of y kilometers per hour, what is y in terms of x?

A. 5x/18
B. 6x/5
C. 18x/5
D. 60x
E. 3,600,000x
y km/h= x m/s = x (1/1000)km/(1/3600)h = 18/5x km/h
Hence, y=18/5x
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by LevelOne » Sat Jul 04, 2009 4:19 am
great thanks, ur answers are correct.
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by shibal » Sat Jul 04, 2009 3:15 pm
how did you Q3?
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by jjk » Mon Jul 06, 2009 9:15 pm
shibal wrote:how did you Q3?
1 meter = 1 thousandth of a kilometer

So knowing that x is in meters/second, you must divide x by 1000. At this point, you are expressing x in terms of kilometers/second.

1 second = 1 thirty-six hundredth of an hour

Knowing that there are 3600 seconds in one hour, you must multiply x by 3600.

So by multiplying x by 3600 and dividing by 1000, you are now expressing x in terms of kilometers per hour.

3600x/1000 reduces to 18x/5, which is C.
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