How many ml of 20 percent acid should be added to pure acid to make 70 ml of 30 percent acid?

61.25%

Step-by-step explanation:

How many ml of 20 percent acid should be added to pure acid

to make 70 ml of 30 percent acid?

:

let x = amt of 20% mixture

then

(70-x) = amt of pure acid

:

0.20x + (70-x) = 0.30 (70)

0.20x + 70 - x = 21

= 21 - 70

-0.8x = -49

x = 61.25%

x = + 61.25 ml of 20% stuff