Martha is carrying her biology, science, and math textbooks. Her books weigh a total of 9 pounds. Her biology textbook weighs 3 pounds and her math textbook weighs 40 ounces. How many ounces does her science textbook weigh?
Answer=56 ounces
First lets find a conversion equation for pounds to ounces...
1pound=16ounces
9pounds=916=144ounces
3pounds=316=48ounces
Given the data, the following equation can be made, where x is equal to the weight of her science textbook.
144=48+40+x
144=88+x
subtract 88 from both sides
56ounces=x
The science textbook weighs 56ounces
9 times 16 is 144 and 3 times 16 is 48.
SO, 144-48= 96
96-40= 56
Her science textbook is 56 oz