To write a decimal as a fraction, first write a fraction with the decimal as the numerator and the integer one as the denominator. Then perform a mathematical operation on the fraction to get rid of the decimal point and simplify the fraction.

Using a fraction with the decimal as the numerator and a denominator of one, such as 3.2/1, eliminate the decimal point. This is accomplished by multiplying both the numerator and the denominator by a power of 10. If there is one decimal place, it will be multiplied by 10. If there are two decimal places, they are multiplied by 100, and so on. There is one decimal place in 3.2, so the numerator and the denominator will be multiplied by 10. The result for this step is 32/10.

Next, simplify the fraction. This is done by dividing both the numerator and the denominator by the highest common factor, or the largest number that each can be divided by without leaving a remainder. In this example, the highest common factor of 32 and 10 is two. Divide 32/2 = 16 and 10/2 = 5. The new fraction is 16/5, which is written as the mixed number 3 1/5.