A parent is 4 times as old as their child. Together they are 80. How old is each?
The child is 16 and the parent is 64.
How to work it out
- 1
Let x be the child's age. The parent is 4 times as old, so the parent is 4x.
- 2
Together they are 80:
- 3
Combine the x terms and divide:
- 4
The parent is 4 × 16 = 64.
- 5
Check: 16 + 64 = 80 ✓ and 64 = 4 × 16 ✓.
LaTeX source of the formulas on this page
\[ x + 4x = 80\ \Rightarrow\ x = 16 \]
\[ x + 4x = 80 \]
\[ 5x = 80\ \Rightarrow\ x = \frac{80}{5} = 16 \]Questions
How old is the child?
16.
How old is the parent?
64.