What is the number between 61 and 107 that is a multiple of 4 10 and 20?
To be a multiple of 4, 10 and 20 the number must be a multiple
of their lowest common multiple.
lcm(4, 10, 20) = 20
What is required is a multiple of 20 between 61 and 107. The
numbers 80 and 100 both satisfy the problem of being between 61 and
107 and being a multiple of 4, 10 and 20.