Question

A baby girl weighed 18 lb 10 oz at 11 months and 20 lb 2 oz at 12 months. How much weight did the baby gain during this month?

Answer 1

1 lb 8 oz

Explanation:

The weight gain was the difference between the current weight and the beginning weight: 20 lb 2 oz less 18 lb 10 oz. Since 10 oz is less than 2 oz, we must 'borrow" 1 lb, or 16 oz, to be able to perform the subtraction. Thus, 20 lb 2 oz becomes 19 lb + 16 oz + 2 oz, or 19 lb 18 oz.

Then the indicated subtraction comes out to 1 lb 8 oz, which represents the baby's weight gain over the past month.