Billy is 11 years older than John. 9 years ago, the sum of their age was 53. How old is John now?
| |
Billy |
John |
Difference |
Total |
| Before |
1 u + 11 |
1 u |
11 |
53 |
| Change |
+ 9 |
+ 9 |
|
+ 18 |
| After |
1 u + 20 |
1 u + 9 |
11 |
2 u + 29 |
The difference in the age between Billy and John remains unchanged.
John's current age = 1 u
Billy's current age = 1 u + 11
Combined age of Billy and Johny 9 years ago
= 1 u + 1 u + 11
= 2 u + 11
2 u + 11 = 53
2 u = 53 - 11
2 u = 42
1 u = 42 ÷ 2 = 21
John's current age
= 1 u + 9
= 21 + 9
= 30
Answer(s): 30
