Question

if you have an unknown amount of both 1% and 4% milk. what is the ratio to make 5 gallons of 2% milk?

Answer 1

they have 4% milk??
anyway let x,y be amount of 1%,4% milk respectively
x+y = 5
.01x + .04y = .02*5=.1
trick to get rid of decimals, multiply both equations by 100
100x + 100y = 500
x + 4y = 10
Solve with substitution
x = 10-4y
100(10-4y) +100y = 500
1000 - 400y +100y =500
1000 -300y = 500
-300y = -500
y = 5/3
x = 10-4*(5/3) = 10-20/3 = 10/3
so mixture is made with 10/3 gallons 1% and 5/3 gallons 4%