what is the probability that the sum of two different numbers randomly picked (without replacement) from the set S = {1,2,3,4} is 5

a)1/5

b)3/16

c)1/4

d)1/3

e)1/2

d

explanation: 4.3 = 12 ways to select two numbers

where as 4 ways to select two numbers that sum to 5 (1+4, 4+1, 2+3, 3+2)

4/12 = 1/3

Is their any other way to do this question?

this question is from Nova Gmat math bible...is it a good book for practice? the book is poorly edited but can i use it as a supplement?

## Nova Book

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The method provided in the book is short and simple enough.sana.noor wrote:Is their any other way to do this question?

You can try for 1 - [Not getting a sum of 5], but that will lead to a bit more calculation.

Or you can try the following method which is almost same as the book.

Number of ways to select 2 numbers from 4 = 4

**C**2 = 6

Number of ways to select 2 numbers from the set such that there sum is 5 --> {1 and 4} or {2 and 3} = 2

Hence, required probability = 2/6 = 1/3

The correct answer is B.

Anurag Mairal, Ph.D., MBA

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