The solution to the problem is as follows:
Write the decimal number as a fraction (over 1)
0.336 = 0.336 / 1
Multiplying by 1 to eliminate 3 decimal places
we multiply top and bottom by 3 10's
Numerator (N) N = 0.336 × 10 × 10 × 10 = 336
Denominator (D) D = 1 × 10 × 10 × 10 = 1000 N / D = 336 / 1000
Simplifying our fraction = 336/1000 = 42/125