Question

A chemist plans to mix 10 liters of a 40% acid solution with some 70% to obtain a 50% solution. How much of the 70% solution should be used?

Answer 1

A chemist plans to mix 10 liters of a 40% acid solution with some 70% to obtain a 50% solution

40% = 0.4

70% = 0.7

50% = 0.5

A chemist plans to mix 10 liters of a 40%. So 10 times of 0.4 = 4

Let x be the some amount  of solution of 70%

70% of x = 0.7x

chemist obtain a 50% of solution

Amount of mixture is 10 + x

So 10+x of 50% = (10+x)*0.5

Now we frame an equation

10 * 0.4  + x * 0.7 = (10+x) * 0.5

4 + 0.7x = 5 + 0.5x

Subtract 4 and 0.5x on both sides

0.2 x= 1

Divide by 0.2

So x= 5

5 liters of 70% of solution is used.