Instructions. In this activity, we are going to subtract fractions in which one denominator is not a multiple of the other. That is to say, their LCM is not one of the numbers.

Step 1: Check the Subtraction box at the top left to begin.

Step 2: Change the red fraction to 3/4, and the blue fraction to 1/3.

Step 3: Pull the black slider to the top and observe what portion of the red circle overlaps.

Step 3: To find the overlapping portion, check the Lowest Common Denominator box. The circle is now divided into equal sectors.

Step 4: Before checking the answer, count the number of overlapping parts.

Step 5: Click on the reset button at the top right, and check the Subtraction box again.

Step 7: Change the red fraction to 5/6 and the blue fraction to 1/4, and repeat the process.