1st Year Maths
Metric System
Centimetres (cm) / Millimetres (mm)
Imperial System
Inches / 1/8 inches
How many Millimetres in a centimetre?
1cm = 10mm
How many centimetres in a metre?
1m = 100cm
Write the following as
centimetres:
(i)
(ii)
(iii)
(iv)
(v)
(vi)
40mm
65mm
15cm 7mm
76mm
1.2metres
3.5metres
Answers:
(i) 40mm = 4cm
(ii)65mm = 6.5cm
(iii)15cm 7mm = 15.7cm
(iv)76mm = 7.6cm
(v) 1.2m = 120cm
(vi)3.5m = 350cm
First we need to find he length of each side by
counting the squares.
8
cm
6
cm
6
cm
The distance
around the
outside of a
shape is called
the perimeter.
8
cm
The perimeter of the shape is 8 + 6 + 8 + 6 =
28cm.
18cm
18cm
What is the perimeter
of each of these
shapes?
22cm
18cm
26cm
Now find the
perimeter of
these shapes.
They are not
drawn to scale.
5cm
3cm
3cm
4cm
3cm
7cm
3cm
7cm
3cm
3cm
Perimeter = 18cm
4cm
3cm
3cm
3cm
3cm
4cm
4cm
3cm
Perimeter = 22cm
Perimeter = 28cm
Area of Rectangle = Length x Width
Q: Find the length of the square.
AREA = 64cm2
1. What do we know about the length
of each side of the square?
2. What number would we have to
multiply by itself to give us an area
of 64cm2?
Answer = 8cm x 8cm = 64cm2
Q: Find the length of this rectangle
8cm
Area = 72cm2
1. What information do we
know about the
rectangle?
2. Because Area = L x W.
We must decide what
number we multiply 8cm
by to get an answer of
72cm2.
3. Answer = 9cm
Q: How can we find the area of this shape?
4cm
7cm
9cm
6cm
2cm
10cm

Split the shape into two rectangles. We know
how to find the area of a rectangle.
4cm
7cm
9cm
B
6cm
A
10cm
2cm

Now find the area of each rectangle and add
them together! Easy!
A
2cm
Area of Rectangle A = L x W
Area = 10cm x 2cm
10cm
Area = 20cm2
4cm
Area Rectangle B = L x W
7cm
B
Area = 4cm x 7cm
Area = 28cm2
Total Area = Area Rectangle A + Area of Rectangle B
4cm
7cm
Total Area = 20cm2 + 28cm2
9cm
Total Area = 48cm2
6cm
2cm
10cm
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Page 154/155/156
Q4
Q7
Q8
Q10
Homework:
Page 154/155
Q3, Q6, Q9
Area of Triangle = ½ Base x Perpendicular Height
8cm
8cm
7cm
10cm
The perpendicular
height means it is
at a right angle to
the base.
8cm
7cm
10cm




Area
Area
Area
Area
of Triangle = ½ Base x Perpendicular Height
= ½ x 10cm x 7cm
= 5cm x 7cm
= 35cm2

Find the value of x in the triangle
Area = 54cm2
x
12cm
1. Examine the information we know
about the triangle. What do we
know?
2. Remember how we find the area of
a triangle: Area = ½ B x H
3. Decide what number we need to
multiply by half of our base of 12cm
to get an answer of 54cm2
4. What will our answer be?
Answer : ½ x 12cm x ? = 54cm2
6cm x ? = 54cm
6cm x 9cm = 54cm
So x = 9cm
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Page 156/157
Q13
Q14,
Q15,
Q16 (iii)
Homework
Page 156/157/158
Q12
Q16 (i) (ii)
Q21