When Mr Bobby is 40 years old, his cousin is 10 years old. In how many years will he be 3 times as old as his cousin?
| |
Mr Bobby |
His cousin |
Difference |
| Before |
40 |
10 |
30 |
| Change |
+ ? |
+ ? |
|
| After |
3 u |
1 u |
2 u |
The difference in the age between Mr Bobby and his cousin at first and in the end remains the same.
Difference in the age between Mr Bobby and his cousin
= 3 u - 1 u
= 2 u
2 u = 40 - 10
2 u = 30
1 u = 30 ÷ 2 = 15
Number of years' time so Mr Bobby will be 3 times as old as his cousin
= 15 - 10
= 5
Answer(s): 5
