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The question for the day is a Math question from the topic Arithmetic Mean.

The average weight of a group of 30 friends increases by 1 kg when the weight of their football coach was added. If average weight of the group after including the weight of the football coach is 31kgs, what is the weight of their football coach in kgs?

1. 31 kgs
2. 61 kgs
3. 60 kgs
4. 62 kgs
5. 91 kgs

The correct choice is (B) and the correct answer is 61 kgs.

The new average weight of the group after including the football coach = 31

As the new average is 1kg more than the old average, old average without including the football coach = 30 kgs.

The total weight of the 30 friends without including the football coach = 30 * 30 = 900.

After including the football coach, the number people in the group increases to 31 and the average weight of the group increases by 1kg.

Therefore, the total weight of the group after including the weight of the football coach = 31 * 31 = 961 kgs.

Therefore, the weight of the football coach = 961 - 900 = 61 kgs.

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