Mrs Tang is 38 years old and her child is 8 years old now. In how many years' time will Mrs Tang be thrice as old as her child?
|
Mrs Tang |
Her child |
Difference |
Before |
38 |
8 |
30 |
Change |
+ ? |
+ ? |
|
After |
3 u |
1 u |
2 u |
The difference in the age between Mrs Tang and her child remains unchanged.
Difference in their age at first
= 38 - 8
= 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 Tang will be thrice as old as her child
= 1 u - 8
= 15 - 8
= 7
Answer(s): 7