Two years ago, Billy's age was 20% of Mark's age. Five years from their current age, Billy's age will be 37.5% of Mark's age. How many years is Mark older than Billy?
| |
Billy |
Mark |
Difference |
| Before |
1x5 =
5 u |
5x5 =
25 u |
4x5 =
20 u |
| Change |
+ 2
+ 5 |
+ 2
+ 5 |
|
| After |
3x4 =
12 u |
8x4 =
32 u |
5x4 =
20 u |
20% =
20100 =
15 37.5% =
3751000 =
38The difference in the ages between Billy and Mark remains unchanged. Make the difference the same. LCM of 4 and 5 is 20.
Increase in Billy's age
= 12 u - 5 u
= 7 u
7 u = 2 + 5
7 u = 7
1 u = 7 ÷ 7 = 1
Number of years that Mark is older than Billy
= 25 u - 5 u
= 20 u
= 20 x 1
= 20
Answer(s): 20
