This is an chemistry problem about calories and i need help do it. Thanks.

Question

Lean ground beef is 20.0% fat, 18.0% protein, and 62% non-caloric components (mostly water). What are the Calories in a 100.0-gram serving of lean ground beef? Give your answer to three significant figures.

Answer 1

You need to know how many calories are in 1 g of fat and 1 g of protein. Looking up these values on the internet, I find...

1 g fat = 9 cal

1 g protein = 4 cal

100.0 g serving x 20% fat = 20 g fat x 9 cal/g = 180 cal

100.0 g serving x 18% protein = 18 g protein x 4 cal/g = 72 cal

Total calories = 180 + 72 = 252 calories (to 3 significant figures) = 0.252 Calories (note the cap C)