Emily's father is 3 times as old as her. Emily will be 16 years old in 4 years' time. In how many years' time will Emily's age be 70% that of her father's?
| |
Emily's father |
Emily |
Difference |
Before
(now) |
3x3 =
9 u |
1x3 =
3 u |
2x3 =
6 u |
| Change 1 |
+ 4 |
+ 4 |
|
| After 1 |
|
16 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
10x2 =
20 u |
7x2 =
14 u |
3x2 =
6 u |
70% =
70100 =
710 Emily's father : Emily = 10 : 7
The difference in age between Emily's father and Emily always remains the same. Make the difference in age between Emily's father and Emily the same. LCM of 2 and 3 is 6.
3 u + 4 = 16
3 u = 16 - 4
3 u = 12
1 u = 12 ÷ 3 = 4
Number of years' time when Emily's age will be 70% that of her father's
= 20 u - 40
= 20 x 4 - 40
= 80 - 40
= 40
Answer(s): 40
