TOPIC
24
Using Percentages
Strand: Number
Strand unit: Percentages
Curriculum Objectives
618 Solve problems relating to profit, loss, discount, VAT, interest, increases, decreases.
Looking back: What the 5th class programme covered
1. Problem solving with simple percentages.
2. Simple discount and increase problems.
Maths skills used in this topic
1. Reasoning: Reason, investigate and hypothesise with patterns and relationships in mathematics.
2. Understanding and recalling: Understand and recall facts, definitions and formulae.
Concrete materials
Calculator
Vocabulary
Cost price, selling price
Teaching points
1. Some of the material in this unit is among the most challenging on the 6th class syllabus.
Keep the numbers small when teaching initial concepts. Finding the cost price when given
the selling price is especially difficult.
2. Ensure that the children are familiar with the most common percentages expressed as
fractions – half, thirds, quarters, fifths, sixths, eighths and tenths (see page 95 of the textbook).
Oral and mental activities
Fans:
Increase €48, €56, €91, etc. by 10%. Repeat with a variety of numbers. Decrease €44, €22, €76,
etc. by 50%. Repeat with a variety of numbers. Introduce harder calculations as the children show
competency in the lower ones. Increase and decrease by 33 13 % ( 13 ) 12 12 % ( 18 ).
Topic suggestions
1. It may be a worthwhile exercise to compare money profit and percentage profit.
For example, which is better: a profit of €10 or a profit of 10%? The question cannot be
answered because it’s being asked in a vacuum. It depends on what was paid for the item.
If the item cost €50, then the €10 profit is preferable (as a 10% profit only equates to €5).
However, if I paid €400 for the item, then the 10% figure represents a greater profit.
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2. The simple interest formula might be introduced to the higher attainers in your class.
PxRxT
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P stands for ‘principal’, the sum of money invested.
R stands for the ‘rate’ (%) at which the money was invested.
T stands for the ‘time’ (years).
Activity A
The wheels have been constructed in such a way that any percentage in the left-hand circle
may be easily computed of any quantity in the right-hand circle (mental arithmetic). You can
use the colours to ‘spice up’ the questions, e.g. ‘What’s the red percentage of the yellow
number?’ Choose a colour in the left-hand circle, choose a colour in the right-hand circle.
What’s the answer?
Differentiation
Lower attainers:
Separate activity sheet
Higher attainers:
1. Separate activity sheet
2. Look for ads in the buy and sell columns of newspapers and dedicated magazines. Children
can bring in these columns and base questions on them. Online selling sites such as eBay may
be of interest.
Topic
Topic
24
24
1. Calculate the profit in money and as a percentage on each item.
1. Sports Goods Bought and Sold. Fill the blanks in the table.
Cost Price
€48
€20
€35
€60
€21
€80
€63
€66
Selling Price
€54
€25
€42
€90
€28
€88
€70
€77
Profit €
€54 – €48 = €6
6
48
Profit %
=
1
8
= 12 12 %
Cost Price
€72
€48
€44
€72
€45
€42
€60
€75
€60
Selling Price
€84
€60
€66
€81
€54
€56
€66
€90
€78
Profit €
Profit %
2. Calculate the loss in money and as a percentage on each item.
Cost Price
€72
Selling Price
€48
€36
€72
€77
€36
€40
€36
€36
€24
€90
€75
€81
€60
Loss %
12
72
Cost Price
€32
€90
€65
€24
€45
€88
€90
€100
€100
Selling Price
€28
€75
€52
€20
€36
€66
€60
€99
€1
Loss €
€60
€88
1
6
Sold For
€ Profit / Loss
% Profit / Loss
€60
€72
€
%
Surf Board
€40
€60
€
%
Badminton Racquet
€20
€18
€
%
Sail Board
€150
€180
€
%
Golf Clubs
€220
€231
€
%
Wet Suit
€30
€27
€
%
Squash Racquet
€98
€112
€
Fishing Rod
€117
€
%
Racing Bicycle
€260
€130
€292.50
€
%
Set of Jerseys
€72
€99
€
%
%
2. Find the cost price of these items. In each case a profit was made.
Example SP: €96
€72 – €60 = €12
=
Bought for
Tennis Racquet
Profit: 20%
100% + 20% = 120% =
1
5
= 16 23 %
= 16
So
5
5
6
5
= 80
= 96
Ans €80
Selling Price
€30
€42
€72
€132
€234
Profit %
20%
20%
20%
20%
20%
€408
20%
€725
€920
€414
€837
25%
25%
12 12 %
12 12 %
Cost Price
Loss €
3. Find the cost price of these items.
Loss %
Selling Price
€572
€891
Profit %
10%
10%
Cost Price
3. Simplify these.
(a)
4x9
15 x 8
____________
(b)
2 x 10
25 x 4
____________
(c)
6x7
35 x 6
____________
(d)
8x5
10 x 16
____________
(e)
9x2
8 x 27
____________
(f)
10 x 12
12 x 10
____________
(g)
5x7
21 x 25
____________
(h)
8x3
9 x 16
____________
(i)
22 x 10
10 x 33
____________
(j)
24 x 11
33 x 36
____________
(k)
50 x 9
9 x 70
____________
(l)
14 x 15
20 x 21
____________
4. Find the cost price of these items. In each case a loss was made.
Example SP: €60
100% – 20% = 80% =
1
5
Cost Price
€143
€228
€338
€414
€500
€683
€800
€920
€950
Selling Price
€139
€215
€540
€399
€315
€725
€699
€635
€499
Profit or Loss €
€4 L
Date: ___________________
= 15
So
5
5
4
5
= 60
= 75
Ans €75
Selling Price
€88
€156
€204
€356
€492
Profit %
20%
20%
20%
20%
20%
€736
20%
Cost Price
5. Find the cost price of these items.
Selling Price
€396
€774
€492
€732
€595
€833
Profit %
10%
10%
25%
25%
12 12 %
12 12 %
Cost Price
Name: _______________________________________
Date: ___________________
© Folens Photocopiables
for a loss.
© Folens Photocopiables
4. Calculate the profit or loss in money in each of these. Write P if a profit has been made or L
Name: _______________________________________
Loss: 20%
Linkage
Measures: Money
Integration
SESE Geography: Human environments – people at work, commerce and trade
Maths at home/parental involvement
Find examples of profit and loss at home – perhaps an older brother or sister bought and sold a
bicycle, Mum or Dad may have traded in a car or bought or sold on an online trading site, etc.
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