Convert the decimal into a whole number by multiplying it by a number with a matching number of zeroes to the figures in the decimal that come after the decimal point. For example, to convert .36 into a whole number, it needs to be multiplied by 100. Write this number as a fraction, with the lower portion being the number you multiplied by. The fraction for our example would be 36/100.
Reduce the size of the fraction by dividing by successive common factors until the fraction is as small as possible. For example, 36 and 100 can both be divided by 4, giving 9/25. Now there are no more common factors, the fraction is as simple as it can become.
Enter the top half of the fraction into the calculator. Press the divide button, and enter the bottom half. Press the equal button and the calculator should now show your original decimal value. If the value in the calculator does not match your original decimal, check to see whether it can be rounded up or down to the correct value.