Adam's age is a multiple of 9 this year.
His age 4 years ago was a multiple of 10.
Adam's age is between 50 and 60.
- 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 4?
(a)
Multiple of 9: 9, 18, 27, 36, 45, 54
Multiple of 9 (-4): 5, 14, 23, 32, 41, 50
Multiples of 10: 10, 20, 30, 40, 50
Adam's age this year = 54
Multiples of 5: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55
Number of years' time when Adam will be a multiple of 5
= 55 - 54
= 1
(b)
Multiples of 4: 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52
Least number of years ago when Adam's age was a multiple of 4
= 54 - 52
= 2
Answer(s): (a) 1; (b) 2