A parent is 3 times as old as their child. Together they are 72. How old is each?
The child is 18 and the parent is 54.
How to work it out
- 1
Let x be the child's age. The parent is 3 times as old, so the parent is 3x.
- 2
Together they are 72:
- 3
Combine the x terms and divide:
- 4
The parent is 3 × 18 = 54.
- 5
Check: 18 + 54 = 72 ✓ and 54 = 3 × 18 ✓.
LaTeX source of the formulas on this page
\[ x + 3x = 72\ \Rightarrow\ x = 18 \]
\[ x + 3x = 72 \]
\[ 4x = 72\ \Rightarrow\ x = \frac{72}{4} = 18 \]Questions
How old is the child?
18.
How old is the parent?
54.