Adam's age is a multiple of 7 this year.
His age 6 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 5?
- How many years ago was Adam's age a multiple of 4?
(a)
Multiple of 7: 7, 14, 21, 28, 35, 42
Multiple of 7 (-6): 1, 8, 15, 22, 29, 36
Multiples of 9: 9, 18, 27, 36
Adam's age this year = 42
Multiples of 5: 5, 10, 15, 20, 25, 30, 35, 40, 45
Number of years' time when Adam will be a multiple of 5
= 45 - 42
= 3
(b)
Multiples of 4: 4, 8, 12, 16, 20, 24, 28, 32, 36, 40
Least number of years ago when Adam's age was a multiple of 4
= 42 - 40
= 2
Answer(s): (a) 3; (b) 2