Question

The average weight of 12 people is 65 kg. If one person leaves and the new average becomes 64.5 kg, what is the weight of the person who left?

• A. 70.5
• B. 80.5
• C. 90.5
• D. 60.5

Answer 1

Answer:

A. 70.5

The total weight of 12 people is:

$12 \times 65 = 780 \text{ kg}$

After one person leaves, there are 11 people with an average weight of 64.5 kg.

Their total weight is:

$11 \times 64.5 = 709.5 \text{ kg}$

Therefore, the weight of the person who left is:

$780 - 709.5 = 70.5 \text{ kg}$

Final Answer

$\boxed{70.5\text{ kg}}$