Adam's age is a multiple of 9 this year.
His age 7 years ago was a multiple of 7.
Adam's age is between 60 and 70.
- 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
Multiple of 9 (-7): 2, 11, 20, 29, 38, 47, 56
Multiples of 7: 7, 14, 21, 28, 35, 42, 49, 56
Adam's age this year = 63
Multiples of 5: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65
Number of years' time when Adam will be a multiple of 5
= 65 - 63
= 2
(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) 2; (b) 3