Mrs Yee is 39 years old and her niece is 9 years old now. In how many years' time will Mrs Yee be thrice as old as her niece?
| |
Mrs Yee |
Her niece |
Difference |
| Before |
39 |
9 |
30 |
| Change |
+ ? |
+ ? |
|
| After |
3 u |
1 u |
2 u |
The difference in the age between Mrs Yee and her niece remains unchanged.
Difference in their age at first
= 39 - 9
= 30
Difference in their age in the end
= 3 u - 1 u
= 2 u
2 u = 30
1 u = 30 ÷ 2 = 15
Number of years time that Mrs Yee will be thrice as old as her niece
= 1 u - 9
= 15 - 9
= 6
Answer(s): 6
