UPSC Prelims 2000 · General Studies

Question 131: Basic Numeracy

The monthly income of Komal and Asha are in the ratio of 4 : 3. Their monthly expenses are in the ratio of 3 : 2. However, both save Rs. 600 per month. What is their total monthly income?

aRs. 8,400

bRs. 5,600

cRs. 4,200

dRs. 2,800

AnswerThe answer is (c).

Let the incomes be 4x and 3x and the expenses 3y and 2y. Both save Rs 600, so 4x - 3y = 600 and 3x - 2y = 600. Doubling the first and tripling the second gives 8x - 6y = 1200 and 9x - 6y = 1800, so x = 600. The incomes are Rs 2,400 and Rs 1,800, a total of Rs 4,200.

Why each option is right or wrong

(a) 8,400 is twice the correct total; it fails the Rs 600 savings check.
(b) 5,600 fails the check: the savings would not both be Rs 600.
(c) Right: 2,400 + 1,800 = 4,200.
(d) 2,800 fails the check: the expenses would not be in the ratio 3 to 2.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 2000, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.