Question 1030957
THE FIFTH GRADER SOLUTION:
To make the final solution, 3 parts of water were added to 1 part of the first mixture.
If those 3 parts were 120 mL of water, then 1 part was {{{120mL/3=40mL}}} .
The first mixture had 1 part of acid in 5 parts of total mixture (1 part + 4 parts of the 1:4 mixture).
If those 5 parts were 40 mL, then the original 1 part of acid was
{{{40mL/5=highlight(8mL)}}} .
 
MAKING IT LOOK LIKE ALGEBRA:
{{{x}}}= volume of acid used, in mL.
{{{4x}}}= volume of water (in mL) mixed with {{{x}}} mL of acid.
{{{x+4x=5x}}}= volume of 1:4 acid:water mixture, in mL.
{{{5x/120=1/3}}}= ratio of volumes of first mixture to water added to make the final solution.
{{{5x/120=1/3}}} --> {{{(5x)3=1*120}}} --> {{{15x=120}}} --> {{{x=120/15}}} --> {{{highlight(x=8)}}}