To write a proper fraction into a decimal whose denominator is 10 or a power of 10:
1) Count the number of zeros in the denominator of the fraction.
2) Insert a decimal point in the numerator after moving from the right to the left by as many digits as there are zeros in the denominator.
For example: 3/100 = 0.03, as there are two zeros in the denominator of 3/100