Find the number of fractions less than 1 such that, in lowest terms, the denominator is 1000.
All the odd numbers between 1 and 1000 which is 500 numbers. From that you must subtract 100 numbers that end in 5 such as: 5, 25, 35, 45........etc.
So, 500 - 100 = 400 numbers - which is what you want.