Look at this shop tag: a jumper marked €25, with a sticker over it saying 20% off. You hand the shopkeeper a €50 note.

Watch two shop tags on the coin tray. For each one we found the sale price first, then built the change with coins and notes.

To find 20% off the €25 jumper, we take 10% of €25 first, which is €2.50, then double it to get €5 off. That leaves a sale price of €20.

The second tag has a further discount taken off the already-reduced price. Watch how the sale price gets smaller before we count the change.

• A €60 LEGO set at 30% off; you hand over a €50 note; find the sale price, then count the change.
• A €40 jumper at 25% off then €5 more off; you hand over €30; find the sale price, then count the change.
• Centra cereal €4.50 at 20% off, plus Lidl milk €1.20 at full price. You hand over €10; find the total, then count the change.

• A €30 top at 10% off; you hand over a €50 note.
• A €20 game at 25% off; you hand over a €20 note.
• An €18 book at 50% off; you hand over a €10 note.
• A €24 toy at 75% off (a quarter of the price is left); you hand over a €10 note.
• The stretch: a €40 jacket at 50% off, then a further 50% off the already-reduced price; you hand over €20.