# If we reduce price by 5€ down to 20€, how many % is that? What is 20% of 15?

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by Olympian (1.9k)

Easy percentages:

Thanks to The Organic Chemistry Tutor

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by Guru (6.1k)
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Percentages

Often when we are bored at school, we may question the purpose of studying. Why do we learn math? Why is it important that I know how to calculate? There are calculators on all smart phones nowadays!

Percentages are a good example of something you need to be able to calculate approximately quickly in your head. Let’s prove this with an exercise.

Tick each one you have seen, experienced or heard about

• 50% discount on all furniture!
• Use the discount code MATHEMATICS and get a 25% discount!
• Your screen time increased by 20% this week
• One third of all students sleep too little during the weekend
• Manchester United’s possession of the ball was 70% against FC Barcelona
• There was a 5% increase in oil prices last year

Let’s learn the theory:

Now that you’ve got an idea how to calculate percentages, have a look at the exercises below. Learning is best done practical projects so get ready to do some crafts as well!

First, make a geoboard according to the instructions on this video. You will have to do some problem solving of your own as well, because the geoboard you need, should have 10 x 10 squares. The geoboard will come in handy when learning geometry, so don’t lose it!

How to make a geoboard

With a rubber band, create an area on the geoboard that covers an area of the whole board according to the percentages mentioned below.

1. How much money is 25% out of 400€?

2. 43% of peanuts is fat. How much fat is there in 200g of peanuts?

3. There are 12 boys and 14c girls in a class. How many percent of the class are,

• Boys?
• Girls?

4. Out of 1500 visitors to an amusement park 30% were 8th graders. Out of those 8th graders, 40% were girls. How many 8th grade girls visited the park?

5. A movie ticket costs 12,50€. The price was raised by 6%.

• What was the price after the increase?
• How much was the increase in euros?

6. The price of a pair of shoes was 67€ and it got raised by 8€. How many percent was the increase?

7. There’s a sale in a furniture store. You can buy a dinner table now for 455,90€ or pay in monthly installments of 42,80€/month (12 months). How many percent more expensive will the table be when you pay for it in instalments?