Make the overlap. Take two strips of paper the same length. Fold one into halves and colour one half. Fold the other into quarters and colour three of them. Lay one across the other on a window or a lamp. Count the squares where both colours cross. That is three quarters of a half.

Before chapter 3. Beto thinks three quarters of a half is a half take away a quarter. Is he right?

The answer. No. "Of" means times. Three quarters of a half is 3/4 × 1/2 = 3/8. A half take away a quarter is only a quarter, which would make 6 rolls instead of 9. In the book, three eighths of the 24-roll recipe is 9 rolls, 150 g of noodles, 3 carrots and 6 sprigs of mint.

The recipe: summer rolls (makes 9). 9 sheets of rice paper, 150 g of thin rice noodles (soaked as the packet says), 3 carrots cut into thin sticks, 6 sprigs of mint, and a little lettuce. Dip each sheet in warm water for a few seconds, lay it flat, fill, fold in the sides and roll. A grown-up handles the hot water and any knife work.

The grown-up layer. Children often expect multiplying to make things bigger. A fraction of a fraction makes things smaller, and the overlap of two strips shows why. FractionForge's Times does the same.

For the ride home. Ask: what is half of a half?