Adding & Subtracting Fractions — Free KS3 Worksheet

Fractions add easily when the pieces are the same size. Three eighths plus one eighth is four eighths, because eighths are eighths. All the difficulty in this topic comes from what to do when the pieces are different sizes, and the answer is always the same: make them match first, then add the tops.

What is on the sheet

It opens with same denominators, so the adding itself is never in doubt. Then pairs where one bottom divides into the other, which needs only one fraction changed. Then full common denominator questions where both have to move. A mixed number stretch follows, and two word problems close it. Every answer in the key is given in its simplest form, so a correct but unsimplified answer is worth a conversation rather than a cross.

Marking it

The adding and subtracting fractions lesson starts from why the pieces have to match, rather than from the procedure.