How many 2-digit numbers are multiples of 5 but not 4?

Quick Answer: 14

Remark

The numbers you are describing can end in 5. But there are others as well. They are t = 10 + 20*n where n goes from 0 to 4. So if n is 4 that means that t = 4*20 + 10 = 80 + 10 = 90.

Solution

15 25 35 45 55 65 75 85 95 are all divisible by 5 but not 4

10 30 50 70 90 are all divisible by 5 but not 4