Simplest form

In the last lesson, you found that nine twelfths is equal to three quarters. We divided the numerator and the denominator by 3. Today, we will write a fraction in its simplest form. Mei cuts a banana cake into 12 equal slices. She gives away 8 slices. What fraction of the banana cake does she give away? Give your answer in its simplest form. Here is the banana cake as one whole bar. Mei cuts it into 12 equal slices. She gives away 8 slices. So she gives away eight twelfths of the banana cake. Can 8 and 12 both be divided exactly by the same number? Yes, both are in the 2 times table. So we group the slices in twos. 8 divided by 2 is 4. 12 divided by 2 is 6. We copy the bar below. Each group of two becomes one bigger part. Now there are 6 equal parts, and 4 are shaded. Can 4 and 6 both be divided exactly by the same number? Yes, by 2 again. So we group the parts in twos again. 4 divided by 2 is 2. 6 divided by 2 is 3. We copy the bar below again. Each group of two becomes one bigger part. Can 2 and 3 both be divided exactly by the same number? Only by 1. So two thirds is in its simplest form. Mei gives away two thirds of the banana cake.

A chocolate bar has 10 equal squares. Kavin eats 6 squares. What fraction of the chocolate bar does he eat? Give your answer in its simplest form. Try it first. Pause if you like. Here is the chocolate bar, with 10 equal squares. Kavin eats 6 squares. So he eats six tenths of the chocolate bar. 6 and 10 can both be divided exactly by 2. 6 divided by 2 is 3, and 10 divided by 2 is 5. We copy the bar, and join every two parts into one bigger part. Only 1 divides both 3 and 5, so three fifths is in its simplest form. Kavin eats three fifths of the chocolate bar.

A paper strip has 18 equal parts. Lin colours 6 parts. What fraction of the strip does she colour? Give your answer in its simplest form. Try it first. Pause if you like. Here is the strip, with 18 equal parts. Lin colours 6 parts. So she colours six eighteenths of the strip. 6 and 18 can both be divided exactly by 2. 6 divided by 2 is 3, and 18 divided by 2 is 9. We copy the bar, and join every two parts into one bigger part. Can 3 and 9 both be divided exactly by 2? No, but both can be divided exactly by 3. 3 divided by 3 is 1, and 9 divided by 3 is 3. We copy the bar, and join every three parts into one bigger part. Only 1 divides both 1 and 3, so one third is in its simplest form. Lin colours one third of the strip. Divide the numerator and the denominator by the same number. Stop when only 1 divides both.