Adam's age is a multiple of 9 this year.
His age 8 years ago was a multiple of 8.
Adam's age is between 70 and 80.
- In how many years' time will Adam's age be a multiple of 5?
- How many years ago was Adam's age a multiple of 5?
(a)
Multiple of 9: 9, 18, 27, 36, 45, 54, 63, 72
Multiple of 9 (-8): 1, 10, 19, 28, 37, 46, 55, 64
Multiples of 8: 8, 16, 24, 32, 40, 48, 56, 64
Adam's age this year = 72
Multiples of 5: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75
Number of years' time when Adam will be a multiple of 5
= 75 - 72
= 3
(b)
Multiples of 5: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70
Least number of years ago when Adam's age was a multiple of 5
= 72 - 70
= 2
Answer(s): (a) 3; (b) 2