How many numbers between 1 and 175 are divisible by 3?

Answer 1

Every third number in a series of numbers is divisible by 3 (i.e. 1,2,3,4,5,6,7,8,9... and so on).

Therefore, the number of numbers divisible by 3 from 1 to any number is the last multiple of 3 which is smaller than that number, divided by 3. This can be realized by doing some simple algebra:

1x3=3, 2x3=6, 3x3=9, ..., Nx3=174 -> N=174/3=58

Note that 174 is the last multiple of 3 before reaching 175.