There are 18 numbers divisible by 5 between 1 and 90.
According to the provided reference, 90 is the eighteenth multiple of 5. This means that the numbers 5, 10, 15, ..., 90 are all divisible by 5, and there are 18 such numbers within the specified range. Therefore, the number of favorable cases for a number divisible by 5 is 18.
