How to Reduce a Fraction to Lowest Terms

A fraction consists of two numbers separated by a line. The number above the line is the numerator. The number below the line is the denominator. If the numerator and denominator are divisible by the same number greater than one, you can reduce the fraction to lowest terms. For example, 3/7 can't be reduced to lowest terms, while 2/4 can be reduced to 1/2.

Instructions

1. To reduce a fraction to lowest terms, find a number that divides evenly into both the numerator and the denominator.

2. A number is divisible by two if the last digit is even (ends in 2, 4, 6 or 8).

3. A number is divisible by three if the sum of the digits is a number divisible by three (ie. 3, 6, 18, 33).

4. If the last digit is zero or five, then the number is divisible by five.

5. If the last digit is zero, then the number is divisible by 10.

6. Choose an example problem: 420/560.

7. Both numbers end in zero, so they are divisible by 10: 420 divided by 10 is 42. 560 divided by 10 is 56. 42/56.

8. Both numbers are even, so they are divisible by two: 42 divided by 2 is 21. 56 divided by 2 is 28. 21/28.

9. Both numbers are divisible by seven. 21 divided by 7 is 3. 28 divided by 7 is 4. 3/4.

10. Reduced to lowest terms, 420/560 is 3/4.

Tips & Warnings

• If you are pressed for time, there are shortcuts you can use. For example, 420/560 is divisible by 20. Dividing by 20 would take less time than dividing by 10 then dividing by two.

Resources

• Purple Math: Reducing Fractions