Video narration
You're at the table, ready for a pizza snack. The pizza is cut into two equal pieces, and you get one. That piece is one half: one of two equal parts. There is one piece left. Then someone gives you the other piece. Put the pieces side by side. Are they the same size? Yes. Each is half of the same pizza. They're the same size, so put the two halves together: one whole pizza! Bring their straight edges together. The round pizza is back! You started with one half, then got one more half. You added the pieces, and they filled the pizza. You can still see the line where the slices meet, but together they cover the pizza. There's no gap, and no extra piece left over. Remember: the two halves fill the whole pizza.