Imagine a round soda bread fresh from the oven, and four of you are going to share it fairly. What do we call one of those pieces? And here is the tricky part: why must all four pieces be exactly the same size?

Watch as one whole pizza is cut into equal parts, again and again. Each time, count the equal parts and see what one piece is called. Notice what happens to the size of a piece as the number of parts changes.

The top number tells us how many to shade

So far we shaded just one piece each time. But the top number of a fraction tells us how many pieces to shade. Watch: here the whole is cut into 3 equal parts, and this time we shade two of them. That is two thirds, written ⅔. The bottom number, 3, is how many equal parts; the top number, 2, is how many we shade.

When I call out a fraction, let's slice the pizza into that many equal parts and shade one piece. We'll make a half, a quarter, a third and a fifth — and say each fraction out loud before we check it.

Today we work through these fractions together: show one half, then one quarter, then one third, then two thirds. Each time, slice the pizza into equal parts and shade the right number of pieces, then check.

What we learned today

• A fraction names equal parts of one whole.
• The bottom number, the denominator, tells how many equal parts the whole is split into.
• The top number tells how many of those parts we shade.
• The parts must all be the same size, or it is not a fraction.