Word problem Help

Question

A lab has 200 L of solution that is 40% acid. The technician needs a solution with 25% acid. How many liters of water must be added to make a solution that is 25% acid?

Answer 1

200 L of 40% + x L of water (0%) = 200+x L of 25%

200(.4) + x(.0) = (200+x).25

200(.4) + 0 = .25(200+x)

80 = 50 +.25x

x = (80-50)/.25 = 30/.25

x= 120 L of water

mix 120 L of water with 200 L of 40% to get 320 L of 25%

another less conventional way to solve the problem:

40-25 = 15

25-0 = 25

25/15 = 5/3

x/200 = 3/5

x= 600/5

x = 120 L

200/120 = 5/3= 25/15