Add and subtract fractions and mixed numbers with like denominators (grade 4) · lesson

Same bottom: add or subtract the tops

💡 When the bottoms match, add or subtract the tops and keep the bottom the same.

4/9 and 3/9 are both ninths. 4 ninths plus 3 ninths is 7 ninths.

The bottom tells the size of the pieces. Adding pieces does not change their size, so the bottom stays the same.

🧠 Let's work it out

Find 4/9 + 3/9.

What do you think comes next?

💡 Add the wholes, add the fractions, and trade a full whole if the fraction part is too big.

A mixed number has a whole part and a fraction part, like 3 5/6.

Add the wholes. Then add the fractions. If the fraction is 1 or more, trade it for a whole.

🧠 Let's work it out

Find 3 5/6 + 1 2/6.

What do you think comes next?

💡 If the top fraction is too small to subtract from, trade one whole for its fraction pieces first.

In 4 1/5 − 1 3/5, you can't take 3/5 from 1/5. So trade 1 whole for 5/5. Now 4 1/5 is 3 6/5.

A whole number works the same way. 3 is 2 5/5 if you need fifths.

For a story with two amounts taken away, add those amounts first. Then take them from the start.

🧠 Let's work it out

Find 4 1/5 − 1 3/5.

What do you think comes next?