Hilda's mother is 3 times as old as her. Hilda will be 18 years old in 6 years' time. In how many years' time will Hilda's age be 70% that of her mother's?
| |
Hilda's mother |
Hilda |
Difference |
Before
(now) |
3x3 =
9 u |
1x3 =
3 u |
2x3 =
6 u |
| Change 1 |
+ 6 |
+ 6 |
|
| After 1 |
|
18 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
10x2 =
20 u |
7x2 =
14 u |
3x2 =
6 u |
70% =
70100 =
710 Hilda's mother : Hilda = 10 : 7
The difference in age between Hilda's mother and Hilda always remains the same. Make the difference in age between Hilda's mother and Hilda the same. LCM of 2 and 3 is 6.
3 u + 6 = 18
3 u = 18 - 6
3 u = 12
1 u = 12 ÷ 3 = 4
Number of years' time when Hilda's age will be 70% that of her mother's
= 20 u - 42
= 20 x 4 - 42
= 80 - 42
= 38
Answer(s): 38
