GATE 2021 CS (CS2) – Question 8

General Aptitude · Quantitative Aptitude: Algebra, Geometry and Mensuration · 2 marks · Multiple choice

Three classes initially have student counts in ratio 3:13:6. Adding 18 to every class changes the ratio to 15:35:21. Find the initial total.

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Correct answer: (C) 88

Explanation

Write initial counts as 3k,13k,6k and new counts as 15m,35m,21m. Subtract the first equation from the second: 10k=20m, so k=2m. Then 3k+18=15m gives 6m+18=15m, m=2 and k=4. Initial total is 22k=88, C.

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