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Mathematics · Ratio, proportion and percentages

Percentages in everyday life

Is 20% off a better deal than 50 TL off? Learn that a percentage is a ratio with denominator 100, work out discounts and price rises, avoid the trap of successive percentages, and take a first look at simple interest.

  • 20 min
  • 1 simulation
  • Mini quiz

Updated:

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The question

Mert wants to buy new trainers. The trainers cost 300 TL in two shops. The first shop's window says "20% off", the second shop's window says "50 TL off". Which shop should Mert buy from? Would the answer change if the price were 200 TL?

Try it yourself

No account needed: change the values and check your answer. Some simulations ask for a prediction before they start; it doesn't matter whether it's right or wrong.

Number line

Discounted price

Drag the point or use the buttons to move in steps of 5 TL. When you reach the right value, press Check.

Prediction

Predict first

How much do you think comes off the ball's price with 25% off?

It doesn’t matter whether you’re right; the simulation opens once you choose.

The rest of the lesson is waiting for you, with a mini quiz.

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Frequently asked

5 questions

If a price goes up by 20% and then down by 20%, is it back where it started?

No. Each percentage is worked out from the price at that moment. A 100 TL item becomes 120 TL after a 20% rise; a 20% discount is now 20% of 120 TL, which is 24 TL. The final price is 96 TL, 4% cheaper than at the start.

Which is better, a percentage discount or a fixed discount?

It depends on the price. On 300 TL shoes, a 20% discount is 60 TL, which beats a 50 TL discount; if the price were 200 TL, 20% would be only 40 TL. A percentage discount grows or shrinks with the price, while a fixed discount always stays the same.

How can I work out a percentage in my head?

For 10%, divide the number by 10: 10% of 300 is 30. 5% is half of that (15), 20% is double (60), and 50% is half the number (150). Combine these pieces to get other percentages: 15% = 30 + 15 = 45.

Why do I pay 75% of the price with a 25% discount?

The full price is 100%. Take away 25% and 100% − 25% = 75% is left. That is why you can find the sale price of a 240 TL coat in one step: 240 × 75/100 = 180 TL.

Can a percentage be more than 100?

Yes. A percentage is a ratio with a denominator of 100, so 150% means 150/100 = 1.5. If a price doubles, it has gone up by 100% and the new price is 200% of the old one. But a part of a whole, such as the share of correct answers in a test, cannot be more than 100%.