Mark's father is 3 times as old as him. His father will be 35 years old in 8 years' time. In how many years' time will Mark's age be 70% that of his father's?
| |
Mark's father |
Mark |
Difference |
Before
(now) |
3x3 =
9 u |
1x3 =
3 u |
2x3 =
6 u |
| Change 1 |
+ 8 |
+ 8 |
|
| After 1 |
35 |
|
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
10x2 =
20 u |
7x2 =
14 u |
3x2 =
6 u |
70% =
70100 =
710 Mark's father : Mark = 10 : 7
The difference in age between Mark's father and Mark always remains the same. Make the difference in age between Mark's father and Mark the same. LCM of 2 and 3 is 6.
9 u + 8 = 35
9 u = 35 - 8
9 u = 27
1 u = 27 ÷ 9 = 3
Number of years' time when Mark's age will be 70% that of his father's
= 20 u - 35
= 20 x 3 - 35
= 60 - 35
= 25
Answer(s): 25
