Numeracy
Application of Number
______________
L1
Workbook 7
Percentages
N2/L1.8
N2/L1.9
N2/L1.10
basic & keySKILLBUILDER
Number
Percentages
N2/L1.8
Rule
Percent = out of every hundred.
50% =
50
100
=
1
2
25% =
100% = the whole amount.
25
100
=
1
4
75% =
75
100
=
3
4
Examples
25% off!!!
A notepad costs £1
25%(
1
4
) of £1 = 25p
£1 – 25p = 75p
The sale price of the notepad is 75p
A CD normally costs £10
25% of £10 = £2.50
£10 - £2.50 = £7.50
The reduced price of the CD is £7.50
Exercise 1
1.
A pack of envelopes costs £1
50% off!!!
2.
50% of £1
= ……….p
£1 - …….
= ……….p
The sale price of the envelopes is ……….p
A plant costs £10
50% of £10 = £……….
£10 - ……. = £ ……….
3.
Huge savings today, 75% off!!!
A pack of Christmas cards costs £1
75% of £1
4
The sale price of the plant is £……….
= ……….p
You will have saved ……….p
You will save £ ……….
A bottle of aftershave costs £10
Workbook 7
Level 1: Numeracy/Application of Number
2
© West Nottinghamshire College 2004
basic & keySKILLBUILDER
Number
Percentages
N2/L1.8
You earn £100 per week.
If you had a pay rise of 25% then you would get an extra 25p for each £1 you earn.
As you earn 100 x £1 you will get 100 x 25p extra.
100 x 25p = 2500p (£25.00)
Divide by 100 to find the
value in £s
If you had a pay rise of 50% then you would get an extra 50p for each £1 you earn.
100 x 50p = 5000p (£50.00)
You have a pay rise of 10%
100 x 10p = 1000p (£10.00)
5.
You have a pay rise of 20%
100 x …… p = ……..p (£……..)
6.
You have a pay rise of 5%
100 x …… p = ……..p (£……..)
7.
You earn £300 per week. Then you have a pay rise of 10%.
300 x …… p = ……..p (£……..)
8.
You earn £200 per week. Then you have a pay rise of 20%
……. x ……p = ..……p (£……..)
Rule
To calculate the percentage (%) of a number, multiply the number by the % then
divide by 100
Workbook 7
Level 1: Numeracy/Application of Number
3
© West Nottinghamshire College 2004
basic & keySKILLBUILDER
Number
Percentages
N2/L1.8
Let’s forget the £s for the moment and just use the rule.
Remember – multiply the number by the % then divide by 100.
Examples
Find 10% of 250
250 x 10 ÷ 100
Step 1 :
250 x 10 = 2500
Step 2:
2500 ÷ 100 = 25
Answer:
10% of 250 is 25
Find 5% of 340
340 x 5 ÷ 100
9.
Step 1:
340 x 5 = 1700
Step 2:
1700 ÷ 100 = 17
Answer:
5% of 342 is 17
Find 10% of 400
400 x 10 = ……..
10.
…….. ÷ 100 = ……..
5% of 700 is ……...
………………………
……………………...
………………………
……………………...
Find 5% of 200
……………………….
12.
10% of 400 is ……..
Find 5% of 700
700 x …….. = ……..
11.
…….. ÷ 100 = ……..
Find 10% of 200
……………………….
Workbook 7
Level 1: Numeracy/Application of Number
4
© West Nottinghamshire College 2004
basic & keySKILLBUILDER
Number
Percentages
N2/L1.8
Half of the strip is black. We could also say 50%
of this strip is black.
All of this strip is black. We could also say 100%
of the strip is black.
Nearly 100% of this strip is black.
More than 50 % of this strip is black.
Exercise 1
Look at these strips which are partly coloured in black.
A
Choose one of these statements to describe each strip.
B
(i)
More than 50% is black
(ii)
Less than 25% is black
(iii)
Less than 50% is black
(iv)
More than 25% is black
C
D
13.
Strip A is ..............................
14.
Strip B is ................................
15.
Strip C is ................................
16.
Strip D is ................................
Workbook 7
Level 1: Numeracy/Application of Number
5
© West Nottinghamshire College 2004
basic & keySKILLBUILDER
Number
Percentages
N2/L1.8
Of 100 people asked about their drinking habits:
46 drank alcohol at weekends only
23 drank alcohol 3 days a week
15 drank alcohol 4 days a week
10 drank alcohol every day
Remember 1 person = 1% here because there are 100 people altogether.
Complete these statements with a number, choosing from:- 5, 25, 35, 50
17.
Less than
% only drank at weekends
18.
More than
% drank every day
19.
About
% drank 3 days a week
20.
Less than
% drank more than 3 times a week.
A year later the figures were very similar but 50% of those who drank alcohol every day had
stopped drinking altogether.
21.
How many people now drink alcohol every day?
22.
What % is this?
23.
What % of people now drink alcohol at weekends only or not at all?
Workbook 7
Level 1: Numeracy/Application of Number
6
© West Nottinghamshire College 2004
basic & keySKILLBUILDER
Number
Percentages
N2/L1.9,10
Find percentage parts
Study the following calculations and try to understand what is happening.
To work out 10% of 900
10% = 900 x
10
100
Percent = out of every hundred
= 90
10% =
10
100
30% =
30
100
To work out 20% of 900
20% = 900 x
20
100
= 180
or
2 × 10% of 900
therefore 90 x 2 = 180
To work out 5% of 900
5%
= 900 x
5
100
= 45
1
of 10% of 900
2
or
therefore
90
= 45
2
To work out 1% of 900
1% = 900 x
1
100
=9
1
10
or
of 10%
therefore
Workbook 7
Level 1: Numeracy/Application of Number
7
90
=9
10
© West Nottinghamshire College 2004
basic & keySKILLBUILDER
Number
Percentages
N2/L1.9,10
And just a few more:
To work out 50% of 900
50% = 900 x
50
100
= 450
1
of 100%
2
or
therefore
900
= 450
2
To work out 25% of 900
25% = 900 x
25
100
= 225
1
of 100%
4
or
therefore
900
= 225
4
To work out 75% of 900
75% = 900 x
75
100
= 675
or
50% + 25%
therefore 450 + 225 = 675
So to sum up:
1
2
1
1
To find 25% - find then
2
2
To find 50% - you can find
To find 75% - find 50% and 25% and add them together.
10% =
1
10
20% = 2 x 10%
30% = 3 x 10%
5% =
1
of 10%
2
or you can use the formula
number x % ÷ 100
e.g. 20% of 300
300 x
20
100
= 60
You may find that you use different methods in different situations.
Workbook 7
Level 1: Numeracy/Application of Number
8
© West Nottinghamshire College 2004
basic & keySKILLBUILDER
Number
Percentages
N2/L1.9,10
Rule reminder.
To calculate the percentage (%) of a number, multiply the number by the % then
divide by 100
Examples
15% of 300 = 300 x 15 ÷ 100 = 45
18% of 50 = 50 x
18
100
=9
Exercise 2
1.
10% of 300 shirts
2.
75% of 12 kg
3.
30% of 30 kg
4.
5% of 1000 ml
Rule
Increase means add on. Decrease means take off.
The price of a second hand car has decreased by 20% from £1500. What is it worth now?
20% of £1500 = 1500 x 20 ÷ 100 = £300
As it is a decrease:
£1500 - 300 = £1200
If the car had increased by 20%, it would be
£1500 + 300 = £1800.
Another second hand car has also decreased by 20% but the original value was £3500.
As it has decreased
£3500 – (3500 x 20 ÷ 100) = £2800
If the car has increased by 20%, it would be
£3500 + (3500 x 20 ÷ 100) = £4200
Workbook 7
Level 1: Numeracy/Application of Number
9
© West Nottinghamshire College 2004
basic & keySKILLBUILDER
Number
Percentages
N2/L1.9,10
5.
Spud-U-Buy does party packs at a discount (decrease).
100 spuds at a 10% discount
200 spuds at a 20% discount
Spud-chilli cost 85p each
Spud-cheese cost 75p each
Spud-salad cost 70p each
a)
Calculate the cost of 100 spud-chillis. Work out the discount. What will they cost
after the discount is removed?
b)
Calculate the cost, after discount, of 200 spud-salads.
c)
Calculate the cost, after discount of 50 spud-cheeses and 150 spud-chillis
(discount of 20%)
6.
An employee earning £190 a week is offered an increase of either £13·50 or 7%.
Which one would you take?
7.
The cost of a package holiday for an adult is £574. It is 70% of that for a child. Find
the cost of 1 adult and 1 child.
8.
The cost of an £8000 car goes up by 2%. What will its new cost be? What is the
deposit of 10% on the new car?
Workbook 7
Level 1: Numeracy/Application of Number
10
© West Nottinghamshire College 2004