Tuesday, November 8, 2011

TANCET Math - Ratio Proportion

Hi

Ratio proportion is an often tested area in the quant section of the TANCET MBA exam. I have posted a medium level difficulty question on Ratios.

Question

The sum of the ages of 3 friends is 90 years. If 5, 3 and 2 years are subtracted respectively from the ages of the oldest, middle and the youngest the ratio of their ages becomes 8 : 5 : 3. What is the age of the oldest of the 3 friends?
1. 40
2. 48
3. 28
4. 17
5. 45

Correct Answer : 45 years. Choice 5.

Explanatory Answer

Let the age of the 3 friends be a, b and c - a the oldest, b the middle one and c the youngest.

Therefore, a + b + c = 90

The question states that a - 5 : b - 3 : c - 2 :: 8 : 5 : 3
So, a - 5 + b - 3 + c - 2 = 8k + 5k + 3k
Or a + b + c - 10 = 16k ... eqn (1)
Substituting a + b + c = 90 in eqn (1), we get 90 - 10 = 16k
or 16k = 80
Hence, k = 5.

a - 5 = 8k
or a - 5 = 40
Therefore, a = 40 + 5 = 45 years.

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