Adam's age is a multiple of 7 this year.
His age 4 years ago was a multiple of 9.
Adam's age is between 40 and 50.
- In how many years' time will Adam's age be a multiple of 3?
- How many years ago was Adam's age a multiple of 8?
(a)
Multiple of 7: 7, 14, 21, 28, 35, 42, 49
Multiple of 7 (-4): 3, 10, 17, 24, 31, 38, 45
Multiples of 9: 9, 18, 27, 36, 45
Adam's age this year = 49
Multiples of 3: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39, 42, 45, 48, 51
Number of years' time when Adam will be a multiple of 3
= 51 - 49
= 2
(b)
Multiples of 8: 8, 16, 24, 32, 40, 48
Least number of years ago when Adam's age was a multiple of 8
= 49 - 48
= 1
Answer(s): (a) 2; (b) 1