Adam's age is a multiple of 7 this year.
His age 5 years ago was a multiple of 5.
Adam's age is between 30 and 40.
- In how many years' time will Adam's age be a multiple of 4?
- How many years ago was Adam's age a multiple of 9?
(a)
Multiple of 7: 7, 14, 21, 28, 35
Multiple of 7 (-5): 2, 9, 16, 23, 30
Multiples of 5: 5, 10, 15, 20, 25, 30
Adam's age this year = 35
Multiples of 4: 4, 8, 12, 16, 20, 24, 28, 32, 36
Number of years' time when Adam will be a multiple of 4
= 36 - 35
= 1
(b)
Multiples of 9: 9, 18, 27
Least number of years ago when Adam's age was a multiple of 9
= 35 - 27
= 8
Answer(s): (a) 1; (b) 8