Thread: Having trouble figuring out why a certain equation works, any ideas?

Hi All

Given the following numbers

a=2, b=19, c= 3

using the equation:

b/c - (a-1) / c

yields the result of how many numbers between a and b are divisible by c - I have tested this and it seems to work - but I am stumped if I know why?!

b/c gives the amount of times C divides into B using 0 as a base starting point, but what stumps me is the significance of (a-1)/c?

Can anyone give me the break down of it because for reason I just can't get it right in my head!!

Many thanks

The number of multiples of less than or equal to is equal to ( is the floor value function). We want to subtract the multiples of that are strictly less than , which is just .


Therefore the number of multiples of between and , inclusive, is .

Thank you Richard - much appreciated