Adam's age is a multiple of 9 this year.
His age 3 years ago was a multiple of 10.
Adam's age is between 60 and 70.
- In how many years' time will Adam's age be a multiple of 2?
- How many years ago was Adam's age a multiple of 5?
(a)
Multiple of 9: 9, 18, 27, 36, 45, 54, 63
Multiple of 9 (-3): 6, 15, 24, 33, 42, 51, 60
Multiples of 10: 10, 20, 30, 40, 50, 60
Adam's age this year = 63
Multiples of 2: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64
Number of years' time when Adam will be a multiple of 2
= 64 - 63
= 1
(b)
Multiples of 5: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60
Least number of years ago when Adam's age was a multiple of 5
= 63 - 60
= 3
Answer(s): (a) 1; (b) 3