Mrs Pang is 45 years old and her cousin is 9 years old now. In how many years' time will Mrs Pang be thrice as old as her cousin?
| |
Mrs Pang |
Her cousin |
Difference |
| Before |
45 |
9 |
36 |
| Change |
+ ? |
+ ? |
|
| After |
3 u |
1 u |
2 u |
The difference in the age between Mrs Pang and her cousin remains unchanged.
Difference in their age at first
= 45 - 9
= 36
Difference in their age in the end
= 3 u - 1 u
= 2 u
2 u = 36
1 u = 36 ÷ 2 = 18
Number of years time that Mrs Pang will be thrice as old as her cousin
= 1 u - 9
= 18 - 9
= 9
Answer(s): 9
