Question

How many pounds of dog food that is half rice must be mixed with 400 pounds of dogfood that is four fifths rice in order to make a dog food that is three quarters rice?

Answer 1

(1/2)x + (4/5)(400) = (3/4)(x + 400)

10x + 16(400) = 15(x + 400)

10x + 6,400 = 15x + 6,000

5x = 400

x = 80 pounds of half-rice dog food