Final answer:
It will take 100 days for him to grow 3 inches of hair.
Step-by-step explanation:
The hair grows 0.03 inches a day. We need to calculate how many days it will take for the hair to grow 3 inches. To do this, we can set up a proportion:
0.03 inches / 1 day = 3 inches / x days
By cross-multiplying, we get x = 100 days. Therefore, it will take 100 days for him to grow 3 inches of hair.