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 9?
- How many years ago was Adam's age a multiple of 6?
(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 9: 9, 18, 27, 36, 45, 54
Number of years' time when Adam will be a multiple of 9
= 54 - 49
= 5
(b)
Multiples of 6: 6, 12, 18, 24, 30, 36, 42, 48
Least number of years ago when Adam's age was a multiple of 6
= 49 - 48
= 1
Answer(s): (a) 5; (b) 1