How do I explain and show the work for a math word problem of If the baby was 8 lbs. 9 oz. and doubled her weight the first six months

5 lb 11⅓ oz

Step-by-step explanation:

First, convert the weight at birth from pound and ounces to just ounces.

8 lb * 16 oz/lb + 9 oz = 137 oz

The baby doubles its weight in the first six months. That means its weight increases by 137 oz over 6 months. To find how much weight was gained in 4 months, write a proportion.

137 / 6 = x / 4

6x = 548

x = 91 ⅓

The baby gained 91 ⅓ oz in 4 months, or 5 lb 11⅓ oz.