Here is a real shelf-tag from a shop: "€30 jumper — 20% OFF!"

So what do you actually hand over at the till? Is it €10? €24? €28? Have a think before anyone says a number.

Each ratio bar shows a price. The shaded slice is the percent that changes. On a discount bar the rest is what you pay. Watch how the slice gets thinner as the percent gets smaller, and notice which one breaks the pattern.

Today we shade the discount part and read off the price left. We'll work these on the ratio bar together, in this order: first a €60 LEGO set with 30% off, then a €25 jumper with 40% off, and finally a €30 lunch with 15% added on for a group booking. The last one flips the rule — nothing comes off, an extra part is added on instead.

For the €25 jumper, remember the €2.50 we found on the board for 10% of €25. Build 40% from four lots of that amount, then read off what you pay.

Now some real Irish-shop problems. Read each one, spot whether it's a take-off or an add-on, then work it. We'll do them in this order: a Smyths board game on sale, a Centra birthday cake with a service charge added on, a coffee-shop group order with a service charge, a Penneys jumper on sale, and a Dunnes coat on sale.