Question

Monique's teacher has asked her to add acid to 8 gallons of a 32% acid in water solution to get a solution which is 70% acid. How much pure acid should she add?

Answer 1

Answer: There is 10 gallons of pure acid she should added.

Step-by-step explanation:

Since we have given that

Let the amount of pure acid she should add be 'x'.

Number of gallons of 32% acid in water solution added = 8

we get a 70% acid.

According to question, we get that

$x+0.32(8)=0.70(x+8)\\\\x+2.56=0.7x+5.6\\\\x-0.7x=5.6-2.56\\\\0.3x=3.04\\\\x=\dfrac{3.04}{0.3}\\\\x=10.13$

Hence, there is 10 gallons of pure acid she should added.

Answer 2

Let x represent the number of gallons of acid Monique adds to the mixture. Then the total amount of acid will be ...
  0.32*8 + x = 0.70(8 +x)
  2.56 + x = 5.60 + 0.70x . . . . . simplify
  0.30x = 3.04 . . . . . . . . . . . . . . subtract 0.70x+2.56
  x = 3.04/0.30 = 152/15 = 10 2/15

Monique should add 10 2/15 gallons of pure acid.