Ababy gains 11 pounds in its first year of life. the baby gained 4 1/4 pounds during the first four months and 3 1/2pounds in its second four months. how much did the baby gain in the last four months?

The baby gains 3.25lbs in the last 4 months. 

This problem can be solved by simple subtraction. Take the total amount and subtract the 4 month increments in order to find the find 4 months. 

Total = 1st 4 months + 2nd 4 months + 3rd 4 months

11 = 4.25 + 3.5 + 3rd 4 months

11 = 7.75 + 3rd 4 months

3.25 = 3rd 4 months

Amount of weight gain in first year = 11 pounds

A year can be divided into three parts consisting of four months each.

According to the question;

The baby gained 4 1/4 pounds during the first four months and 3 1/2pounds in its second four months.

Let weight gained in third 4 month be 'x' pounds.

So;

=> Weight gained in first year = Weight gained in first 4 months + Weight gained in second 4 months + Weight gained in third 4 months

=> 11 pounds = 4.25 pounds + 3.5 pounds + x pounds.

=> x pounds = 11 pounds - 7.75 pounds

=> x pounds = 3.25 pounds

Therefore, the baby gain 3.25 pounds in the last four months.