Question

The average (arithmetic mean) weight of 3 boxes is 70 pounds. If each box weighs at least 68 pounds, what is the greatest possible weight, in pounds, of one of these boxes?

Answer 1

For one of the boxes to have maximum weight, the other two should have minumum weight.

Explanation:

The total weight of the boxes must be `3xx70=210lbs`

Two boxes of minimum weight: `2xx68=136lbs`

Left over for the third box: `210-136=74lbs`

OR:
Two boxes are allowed to be `2lbs` under the average (each)

This means that one box may be `4lbs` over the average.