Mathematics A butcher

Question

A butcher has some hamburger that is 20% fat and some that is 11% fat. How many pounds of each should be mixed to make 78 lb of hamburger that is 14% fat

Answer 1

20x + 11(78-x) = 14(78)

20x-11x = 14(78)-11(78)

9x = 14(78)-11(78) = 3(78)

x = 3(78)/9 = 26 lbs of 20% to mix with 52 pounds of 11% to get 78 lbs of 14%

20-14= 6

14-11= 3

6/3 =2

1/2 as much 20% is needed as 11%

26/52 = 1/2

.2(26)+.11(52) = 5.2 + 5.72 = .14(78) = 10.92