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Q4 (CISF/2020) Miscellaneous & General Knowledge › Important Days, Places & Events

The average weight of a class is 20 kg. If the strength of the class is increased by 25%, then the average weight of the class gets increased by 1%. What is the average weight of the additional students ?

Result
Your answer: —  Â·  Correct: B

Explanation

Let the initial number of students in the class be n. The initial average weight is 20 kg, so the total weight of the class is 20n.

When the strength of the class increases by 25%, the new number of students becomes n + 0.25n = 1.25n. The average weight of the class increases by 1%, which is 1% of 20 kg = 0.2 kg. Therefore, the new average weight is 20.2 kg.

The new total weight of the class is 1.25n × 20.2 = 25.25n.

The total weight of the additional students is the difference between the new total weight and the initial total weight: 25.25n - 20n = 5.25n.

The number of additional students is 0.25n. Thus, their average weight is:

Average = 5.25n / 0.25n = 21 kg

Hence, the average weight of the additional students is 21.00 kg.

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