الأسبوع 23 · النسبة المئوية من كمية والخصومات ومسائل النسبة · 3 دروس
2
Discounts and increases in everyday shopping
Discover Mathematics P6: Term 2, Unit 10, Lessons 10–11
GoalFind the discount, the sale price and the price after an increase.
New words
discount · the amount taken off the pricesale price · the price you pay after the discountincrease · the amount added to a price
Explanation
A discount of 25% means we take 25% of the OLD price off. First find the discount (25% of the price), then subtract: sale price = price − discount. For an increase it is the same idea, but we add: new price = price + increase. “50% off” means half the price is taken away. It does not mean “50 LE off”. A coat of 180 LE with 50% off loses 90 LE and costs 90 LE. You can also use the leftover percent: with 25% off you pay 75% of the price. Always check that your answer makes sense: a sale price is smaller than the old price, and a price after an increase is bigger.
ƒFormula
Sale price = price − discount New price = price + increase
Worked examples
A school bag costs 240 LE and has 25% off. Discount: 240 ÷ 4 = 60 LE. Sale price: 240 − 60 = 180 LE. (Or 75% of 240 = 180.)
A coat costs 180 LE and is 50% off. Half of 180 is 90, so you save 90 LE and pay 90 LE. “50% off” is not “50 LE off”: that would leave 130 LE.
A school lunch costs 150 LE a month. The price goes up by 10%. Increase: 15 LE. New price: 150 + 15 = 165 LE.
Class activity
Sale detective. Look at a shop leaflet or a sale sign with a grown-up. Find the old price and the percent off. Work out the discount and the sale price in LE, and check your answer against the sign.
Practice
1
A pair of shoes costs 350 LE with 20% off. Find the discount and the sale price.
20% of 350 = 70 LE. Sale price = 350 − 70 = 280 LE.
2
A toy costs 80 LE. The price rises by 5%. What is the new price?
5% of 80 = 4 LE. New price = 84 LE.
3
A jacket costs 600 LE with 15% off. How much do you pay?
10% = 60 and 5% = 30, so the discount is 90 LE. You pay 600 − 90 = 510 LE.
4
A phone costs 2,000 LE. In a sale it is 10% off. What is the sale price?
10% of 2,000 = 200. Sale price = 1,800 LE.
5
A shirt costs 120 LE. Seif says “50% off means I pay 50 LE.” Is he right?
No. 50% of 120 is 60, so he pays 120 − 60 = 60 LE.
