CAT 2021 Slot 3 · Quant · Question 7

CAT 2021 Slot 3 previous year question on Averages, Mixture and Alligation, with the answer and a step-by-step solution.

Averages, Mixture and AlligationArithmeticType in the answer (TITA)Medium
The arithmetic mean of scores of 25 students in an examination is 50. Five of these students top the examination with the same score. If the scores of the other students are distinct integers with the lowest being 30, then the maximum possible score of the toppers is
Answer & solution

Answer: 92

The total of all 25 scores is fixed at 25\times 50=1250.

Five students share the top score T, and the other 20 have distinct integer scores. To make T as large as possible, make the other 20 scores as small as possible.

They must be distinct with the lowest equal to 30, so the smallest they can be is 30,31,32,\ldots ,49. That sums to \frac{20}{2}\left( 30+49 \right)=10\times 79=790.

Then 5T=1250-790=460, so T=92.

This is consistent, since 92 is above the highest of the other scores, 49, so the five really are the toppers.

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