A sample of ground beef contains 21.3% protein and 16.9% fat, both by mass. What mass of this ground beef, in grams, contains 350 Calories? Assume all Calories come from protein and fat.

147.5 grams

Explanation:

Let the required mass of ground beef be m .

protein in it = .213 m

fat in it = .169 m

1 gram of protein gives 4 cals .

1 gram of fat gives 9 cals .

cals given by .213 m protein = 4 x .213 m .

cals given by .169 m fat  = 9 x .169 m .

4 x .213 m  + 9 x .169 m = 350

.852 m + 1.521 m = 350

2.373 m = 350

m = 147.5 grams Ans