1. Calculating percentages mentally
We can use percentages that we know to find other percentages.
Suggest ways to work out:
15%
20%
30%
60% 1%
10%
75%
100%
Discuss how the percentages on the board could be calculated mentally.
For example, to find 20%, find 10% and double the answer or find 1/5 by dividing by 5.
To find 17.5% we can find 10%, half that answer to find 5% and half that answer to find 2.5%. Adding these together give 17.5%. Mention that this is the percentage used to find VAT.
For example, to work out 17.5% of £42:
10% of £48 is £4.80,
5% of £48 is £2.40,
2.5% of £48 is £1.20,
17.5% of £48 is £ £ £1.20 = £8.40.
35%
15%
5 %

2. Recap: Percentages of Amounts Calculate the percentage
of each amount as asked.

3. Find . . .
10% of £460
£46

4. Calculate . . .
20% of 180 36

5. Work out . . .
40% of 70 28

6. Find the answer to . . .
25% of 80 20

7. Evaluate . . .
70% of 50 35

8. Evaluate . . .
5% of 500 25

9. Find . . .
60% of 40 24

10. Work out . . .
80% of 90 72

11. Percentage Increase/Decrease
Increase £ by 10%
10% of
= ÷ 10
= £2400
£ £2400
Total = £26 400

12. Visit each shop and work out the new price of each item Some need to be discounted Some need to be increased

13. £20 000 £75 £4 500 £4 500 20% Increase 1.2 £5 400 £20 000 20% Increase
Multiplier
£4 500
20% Increase
1.2
£5 400
£20 000
20% Increase
1.2
£24 000
£75
20% Increase
1.2
£90

14. 25% off selected products £8 £2 £9 £2 0.75 £1•50 £8 0.75 £6 £9 0.75
25%
off selected products £9 £8 £2
% Increase/ decrease
% Amount (£)
New cost of item
Cost of item
Multiplier
Cereal Variety Pack £2
25% Decrease
0.75
£1•50
Chocolate Cake £8
25% Decrease
0.75 £6
Transformers DVD £9
25% Decrease
0.75
£6•75

15. 15% reductions £60 £25 £50 Clothing £25 0.85 £21•25 £50 0.85 £42•50
15%
reductions
£25
£50
£60
% Increase/ decrease
% Amount (£)
New cost of item
Clothing
Cost of item
Multiplier
T-shirt
£25
15% Decrease
0.85
£21•25
Jeans
£50
15% Decrease
0.85
£42•50
Trainers
£60
15% Decrease
0.85
£51

16. all outdoor sports equipment
30% off
all outdoor sports equipment
£30
£15
£13
% Increase/ decrease
% Amount (£)
New cost of item
Cost of item
Multiplier
Cricket Set
£30
30% Decrease
0.7
£21
Football
£13
30% Decrease
0.7
£9•10
Football Gloves
£15
30% Decrease
0.7
£10•50

17. Utility Bill Increase Rates
British Gas %
EDF Energy %
TV Licence %
% Increase/ decrease
% Amount (£)
New cost of item
Cost of item
Multiplier
British Gas Bill
£302•41
5% Increase
1.05
£317•53
EDF Energy Electricity Bill
£56•66
6% Increase
1.06
£60•06
TV licence
£116
5% Increase
1.05
£121•80

18. £2550
£740
Banking Interest Rates
Halifax Current Account 1%
NatWest Current Account 2%
Lloyds Current Account 0•5%
Halifax Savings Account 3%
NatWest Savings Account •5%
Lloyds Savings Account %
£150
% Increase/ decrease
% Amount (£)
New cost of item
Cost of item
Multiplier
Halifax - Current Account
£740
1% Increase
1.01
£747•40
Lloyds - Savings Account
£2550
3% Increase
1.03
£2626•50
NatWest - Current Account
£150
2% Increase
1.02
£153