SBI PO – 2015 – 30

Question: Weight of two persons A and B are in the ratio of 3 : 5. A’s weight increases by 20% and the total weight of A and B together becomes 80 kg, with an increase of 25%. By what percent did the weight of B increase? [दो व्यक्तियों A तथा B के वजन का अनुपात 3 : 5 है. A का वजन 20% से बढ़ जाता है. यदि दोनों के कुल वजन में 25% की वृद्धि होती है, और यह बढ़कर 80 किग्रा हो जाता है, तो, बताएं कि B के वजन में कितने प्रतिशत की वृद्धि होती है?] [Ans. (a)  28%]

(a)  28% (b)  30%  (c)  45%   (d) 32%     (e) none of these

Detailed Explanation:

First Method: The question can be easily be solved by “Method of Alligation”. Since A’s weight increases by 20%, while total weight increases by 25%. The ratio between the weights is 3 : 5.

The difference between 20 and 25 is 5 and the term of the ratio for B is also 5. So, 5≡5

The term of the ratio for A is 3. So, 3 ≡ 3

Since 20 is less than 25, so “?” (percentage increase in B) must be greater than 25 by 3.

Therefore, ? – 25 = 3. It means, ? = 28. So, 28% Ans.

Second Method: “Without changing the ratio, the values may be changed”.  Since the ratio between the weights of A and B is 3 : 5, so let the weight of A is 300 kg and weight of B is 500 kg; so that the total weight of A and B becomes 800 kg.

Increase in A’s weight = 20% of 300 kg = 60 kg

Increase in total weight = 25% of 800 kg = 200 kg

Increase in B’s weight = 200 kg – 60 kg = 140 kg

140 is the increase out of 500, that is 28% Ans.