Percentages

Write down everything you can about

What other numbers are the same?

Make up some calculations using it

10

6

What Percentages mean?

• The Symbol % means per cent Per cent means out of every 100.cent is the Latin ( and

French) word for 100 and many of our words start with “cent” are something to do with 100.

e.g. century, centimetre etc

Percentages

Today

• Everyone will• Calculate simple percentages of amounts without a

calculator• Calculate any percentage with a calculator• Add or subtract percentage increases or discounts.• Add on VAT• Calculate simple interest over a number of years• Recall common financial terms such as APR• Some people may also be able to• Calculate Compound interest (Not required for

Foundation level)• Calculate reverse percentages (Not required for

Foundation Level)

Percentages of quantities

• Percentages are fractions of 100.• To find 1% of a quantity we divide by 100.

• Example:• find 1% of £230• Answer:• £230 ÷ 100 = £2.30

• What do we do to find 2%?

Percentages of quantities

• Percentages are fractions of 100.• To find 10% of a quantity we divide by 10.

• Example:• find 10% of £230• Answer:• £230 ÷ 10 = £23.00

• What do we do to find 20%?• What do we do to find 5%?

Discuss and complete the statements

• To find 10%• To find 20%• To find 5%• To find 2.5%• To find 17.5%• To find 50%• To find 25%• To find 75%• Are there any percentages you cannot find?

Without a calculator work out

• 10% of £340

• 5% of £40

• 20% of £200

• 25% of £120

• 75% of £2.80

• 75% of 38.44

Without a calculator work out

• 10% of £340 £34

• 5% of £40 £2

• 20% of £200 £40

• 25% of £120 £30

• 75% of £2.80 £2.10

• 75% of 38.44 £28.83

To find any % of any amount

Use a calculator to work out

• 13% of £8.20

• 6% of £240

• 3% of £4.20

• 4.2% of £123.46

• Can you think of a way of cutting out the “divide by 100” step on the calculator??

Use a calculator to work out

• 13% of 8.20 = 1.066

• 6% of £240 = £14.40

• 3% of £4.20 = £0.126 or 13p

• 4.2% of £123.46 = £5.19

• Can you think of a way of cutting out the “divide by 100” step on the calculator??

% on Calculator

• 45% of £320

press keys

4 5 shift % × 320 =

£144

Percentage Increases.

Pay rise• Wage now: £180 weekly

• % increase 3%

• Actual increase 3% of £180 = 180÷100×3 = £5.40

• New wage = 180 + 5.40 = £185.40

Add on the increase at the end

VAT: Value Added Tax

• VAT is now 20%• VAT was 17.5% in the past years.• Without VAT the computer costs =£450• VAT at 17.5 % =17.5×450 =7875÷100• =£78.75

• How much do you pay for the computer?

450+ 78.75 = £ 528.75• How much more will it be when the VAT

goes up to 20%?

VAT

• 20% of %450

Price of computer with 20% VAT=

Discounts

• Coat is usually = £65

• Discount 30% off

30×65 =1950 ÷ 100

= £19.50

• Amount you pay

65 – 19.50 = £45.50

20% off

One number as a % of another

• Write the information as a fraction first

• Simply the fraction if you can

• Multiply the numerator by 100

• Then divide by the denominator

Try these

• In a box of chocolates,10 are soft centred and 15 are not. What percentages of chocolates in the box are not soft centred?

• In April 12 days are wet and rest are dry.

• What percentages of days in April are dry?

(30 days in April)

Try these

• Write 30 cm as percentage of a metre

• Write 300ml as percentages of 2 litres

• Write 45p as a percentages of £2

• write 30 out of 75 as a percentages

Loans & savings

• You get interest if you can put money in a savings account

• APR = annual percentage rate

• Interest is charged on loans.

• Lenders quiz

• Loan rates

One quantity as a percentage of another

Profit and Loss

Profit and loss

Simple Interest

Compound Interest• The interest is added to the capital at the end of each year. For 3 years• Start capital= £3000 Interest rate = 3% p.a

Year Start amount

Interest Amount at end of the year.

1 £3000 3%of 3000= 90 £3090

2 £3090 3% of 3090=£92.70

£3182.70

3 £3182.70 3% of £3182.70= £95.48

£ 3278.18