Penelope's father is 3 times as old as her. Penelope will be 19 years old in 10 years' time. In how many years' time will Penelope's age be 70% that of her father's?
| |
Penelope's father |
Penelope |
Difference |
Before
(now) |
3x3 =
9 u |
1x3 =
3 u |
2x3 =
6 u |
| Change 1 |
+ 10 |
+ 10 |
|
| After 1 |
|
19 |
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
10x2 =
20 u |
7x2 =
14 u |
3x2 =
6 u |
70% =
70100 =
710 Penelope's father : Penelope = 10 : 7
The difference in age between Penelope's father and Penelope always remains the same. Make the difference in age between Penelope's father and Penelope the same. LCM of 2 and 3 is 6.
3 u + 10 = 19
3 u = 19 - 10
3 u = 9
1 u = 9 ÷ 3 = 3
Number of years' time when Penelope's age will be 70% that of her father's
= 20 u - 37
= 20 x 3 - 37
= 60 - 37
= 23
Answer(s): 23
