Elijah's father is 4 times as old as him. His father will be 34 years old in 10 years' time. In how many years' time will Elijah's age be 80% that of his father's?
| |
Elijah's father |
Elijah |
Difference |
Before
(now) |
4x1 =
4 u |
1x1 =
1 u |
3x1 =
3 u |
| Change 1 |
+ 10 |
+ 10 |
|
| After 1 |
34 |
|
|
| Change 2 |
+ ? |
+ ? |
|
| After 2 |
5x3 =
15 u |
4x3 =
12 u |
1x3 =
3 u |
80% =
80100 =
45 Elijah's father : Elijah = 5 : 4
The difference in age between Elijah's father and Elijah always remains the same. Make the difference in age between Elijah's father and Elijah the same. LCM of 3 and 1 is 3.
4 u + 10 = 34
4 u = 34 - 10
4 u = 24
1 u = 24 ÷ 4 = 6
Number of years' time when Elijah's age will be 80% that of his father's
= 15 u - 34
= 15 x 6 - 34
= 90 - 34
= 56
Answer(s): 56
