The average weight of a group of seven boys is 56 kg. The individual weights (in kg) of six of them are 52, 57, 55, 60, 59 and 55…

Question

The average weight of a group of seven boys is 56 kg. The individual weights (in kg) of six of them are 52, 57, 55, 60, 59 and 55. Find the weight of the seventh boy.

1. A. 45 Kg
2. B. 54 Kg (Correct answer)
3. C. 49 Kg
4. D. 58 Kg

Correct Answer

Option B — 54 Kg

Detailed Solution & Explanation

The correct answer is 54 Kg.

Key Points

• Total weight of the seven boys = average x number = 56 x 7 = 392 kg.
• Sum of the six known weights = 52 + 57 + 55 + 60 + 59 + 55 = 338 kg.
• Weight of the seventh boy = 392 - 338 = 54 kg.

Additional Information

• The general relation to memorise is Sum = Average x Count; almost every average question reduces to recovering a missing term from the total.
• A quick check: 54 is just below the 56 average, and the six known weights sum to 2 kg more than 6 x 56 = 336, so the last boy must be 2 kg below average.