Marion's mother is 3 times as old as her. Marion will be 12 years old in 3 years' time. In how many years' time will Marion's age be 70% that of her mother's?
| |
Marion's mother |
Marion |
Difference |
Before
(now) |
3x3 =
9 u |
1x3 =
3 u |
2x3 =
6 u |
| Change 1 |
+ 3 |
+ 3 |
|
| After 1 |
|
12 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
10x2 =
20 u |
7x2 =
14 u |
3x2 =
6 u |
70% =
70100 =
710 Marion's mother : Marion = 10 : 7
The difference in age between Marion's mother and Marion always remains the same. Make the difference in age between Marion's mother and Marion the same. LCM of 2 and 3 is 6.
3 u + 3 = 12
3 u = 12 - 3
3 u = 9
1 u = 9 ÷ 3 = 3
Number of years' time when Marion's age will be 70% that of her mother's
= 20 u - 30
= 20 x 3 - 30
= 60 - 30
= 30
Answer(s): 30
