In a group of 32 students, the average weight was 18.5 kg. When 4 students left the group, the average came down to 15.5 kg. What was the average weight (in kg) of those 4 students?

Correct option is A

Given:

The initial average weight of 32 students is 18.5 kg. After 4 students left, the average weight of the remaining 28 students became 15.5 kg.

Solution:

The total weight of all 32 students:

Total weight of 32 students = 32 × 18.5 = 592 kg

The total weight of the remaining 28 students:

Total weight of 28 students = 28 * 15.5 = 434 kg

The total weight of the 4 students who left the group:

Total weight of 4 students = 592 kg - 434 kg = 158 kg

The average weight of the 4 students:

Average weight of 4 students = 158 kg / 4 = 39.5 kg

Therefore, the average weight of the 4 students who left the group is 39.5 kg.