Everyday Percentages

Most of the population struggle with percentages.

You’re going to come across percentages throughout your life.

I want you to be able to work them out and be confident enough to know that

you’ve got the right answers.

In Numeracy we work with amounts of something (e.g. money, time)

This is one of the ways in which your Numeracy class is different to a traditional

school Maths class where you might get worksheets of calculations to let you

practice something (e.g. dividing a fraction by another fraction).

Three ways to calculate everyday percentages

I’m going to show you three ways to work out a percentage of an amount of

money:

12% of £650

The old way (no calculators)

Depending on what age you are, this how your grandparents would have been

shown.

It makes use of this:

it is easy to divide decimal numbers by 10

if you divide an amount by 10, you’ve found a tenth of it

10% is the same as a tenth

once have 10%, you just divide by 10 again to get 1%

You need 12% of £650 £ 650.00

Divide by 10 to get 10% £ 65.00 (10%)

Divide this answer by 10 again to get 1% £ 6.50 ( 1%)

Combine them to get 12%

10% £65.00

1% £ 6.50

1% £ 6.50

Total £78.00

The “two step” method (calculator)

This is the way that I see most students use.

These days you’ll have a calculator app on your smartphone.

It uses this two step method

divide by 100 to find 1%

multiply the answer by the percentage you need to work out

You need 12% of £650 £ 650.00

Divide by 100 to get 1% £ 6.50 (1%)

Multiply by 12 to get 12% Total £ 78.00 (12%)

The “quickest” method (calculator)This is the quickest way.

Percentages, fractions and decimal numbers (e.g. money) are three ways of

writing the same thing.

They are all an amount OF something.

The word OF means MULTIPLY (people say “times”)

Think about how these three calculations all give the same answer, £0.25

25% of £1.00 a quarter of £1.00 0.25 x £1.00

In this method you write the percentage you want as a decimal and multiply by it.

12% is 0.12 written as a decimal number.

It might help to think of percent as pence where 100% is £1.00

e.g. 25% is 0.25, 3% would be 0.03

You need 12% of £650 £ 650.00

Write 12% as a decimal 0.12

Multiply by it Total £ 78.00 (12%)

Use whichever method works for you and try the following questions.

The ANSWERS are at the end.

CAR INSURANCE – “No Claims Bonus”

Joanne is renewing her car insurance.

She will get a “no claims bonus” of a 15% reduction off the full price as she didn’t

have an accident last year.

This year the full price of her insurance is £630.

Q1. How much will her insurance be with the “no claims bonus”? …………

(Hint: work out the discount then subtract it from the normal cost)

Adding VAT

A new window costs £550. 20% VAT will be added to the cost.

Q2. How much will the final total be (with VAT added)? ………..

(Hint: work out the VAT due then add it to the cost of the window)

Hire Purchase

A new van costs £30,400. You pay a 30% deposit.

Q3. How much is there still left to pay? …………

(Hint: work out the deposit paid then subtract it from the cost of the van)

Estimating future sales

A rock band’s management company keeps a note of how many people attend

the band’s concerts and how many tee shirts are sold.

On the last tour, 12% of concert goers bought a tour tee shirt. This year the band

has another tour and 350,000 tickets have been sold.

Q4. Estimate how many tee shirts they might sell this tour? …………

(Hint: use the percentage of folk who bought a tee shirt last tour to estimate how

many folk will buy tee shirts this year)

Loyalty Card Discount

A cinema runs a loyalty card system. Customers with a loyalty card get a

discount of 15% off ticket prices. Tickets are £7.50 each.

A customer with a loyalty card buys 4 full price tickets.

Q5. How much will the customer be charged? …………

ANSWERS

Q1. Work out the 15% discount 15% of 630 = £94.50

Subtract the discount £630 - £94.50 = £535.50

Q2. Work out the 20% VAT due on £550 20% of £550 = £110

Add the VAT to the cost £550 + £110 = £660

Q3. Work out the 30% discount

30% of £30,400 = £9120

Subtract the deposit paid from the full cost

£30,400 - £9,120 = £21,280

Q4. On the last tour 12% of folk bought tee shirts

Use this to estimate the number they’ll sell this tour

350,000 tickets have been sold

12% of 350,000 = 42,000

Q5. Work out the cost of 4 full price tickets

4 x £7.50 = £30

Work out the 15% discount

15% of £30 = £4.50

Subtract the discount from the full cost

£30 - £4.50 = £25.50