Adam's age is a multiple of 4 this year.
His age next year will be multiple of 5.
Adam's age is between 20 and 30.
- In how many years' time will Adam's age be a multiple of 9?
- How many years ago was Adam's age a multiple of 5?
(a)
Multiples of 4 (between 20 and 30): 20, 24, 28
Multiples of 4 (+1): 13, 17, 21, 25, 29
Multiples of 5: 20, 25, 30
Adam's age next year: 25Adam's age this year: 24Multiples of 9: 18, 27
Adam's age when it becomes a multiple of 9 = 27
Number of years' time when Adam's age will be a multiple of 9
= 27 - 24
= 3
(b)
Multiple of 5: 10, 15, 20
Least number of years ago when Adam's age was a multiple of 5
= 24 - 20
= 4
Answer(s): (a) 3; (b) 4