Indian Institute of Foreign Trade 2010 Solved Paper

Question : 23 of 135

Marks: +1, -0

In a Green view apartment, the houses of a row are numbered consecutively from 1 to 49. Assuming that there is a value of ‘x’ such that the sum of the numbers of the houses preceding the house numbered ‘x’ is equal to the sum of the numbers of the houses following it. Then what will be the value of ‘x’?

Validate

Solution:

It is given that sum of the first

(x-1)

numbers is equal to sum of the numbers from

(x+1)

to 49 or, sum of

(x-1)

numbers = sum of first 49 numbers - sum of first numbers

{x(x-1)}/2={49×50}/2-{x(x+1)}/2

On solving, we get

x=35

Hence, option C is the correct answer.

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