Adam's age is a multiple of 9 this year.
His age 2 years ago was a multiple of 10.
Adam's age is between 70 and 80.
- In how many years' time will Adam's age be a multiple of 7?
- How many years ago was Adam's age a multiple of 7?
(a)
Multiple of 9: 9, 18, 27, 36, 45, 54, 63, 72
Multiple of 9 (-2): 7, 16, 25, 34, 43, 52, 61, 70
Multiples of 10: 10, 20, 30, 40, 50, 60, 70
Adam's age this year = 72
Multiples of 7: 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77
Number of years' time when Adam will be a multiple of 7
= 77 - 72
= 5
(b)
Multiples of 7: 7, 14, 21, 28, 35, 42, 49, 56, 63, 70
Least number of years ago when Adam's age was a multiple of 7
= 72 - 70
= 2
Answer(s): (a) 5; (b) 2