Transcript Y5T2U7D1_2 - Primary Resources

L.O.1
To recall multiplication facts up to 10 x 10
Don’t draw the table just write the missing answers in order in your book.
X
5
5
25
6
7
7
3
9
4
2
6
40
18
28
4
9
8
24
18
2 ½ minutes
Which multiplication facts are hard to
remember?
Why do you think that is?
Which are easy to remember?
L.O.2
To understand area measured in square
centimetres
To begin to understand the formula
“length x breadth” for the area of a rectangle
What do we mean by the word “area”?
Show where the area of your table top is.
REMEMBER…
The area of a 2-D shape is the amount
of surface within its perimeter.
Q. How can we work out the area of this rectangle?
We can do it by counting the squares.
The rectangle has 24 squares
Its area can be written as
24 square centimetres or 24 cm².
Draw 2 rectangles in your book.
Write the dimensions and areas next to each.
Be prepared to explain your working.
Q. Is there a quick way to find the area of a rectangle?
You should find that multiplying the
number of squares in each row by the
number in each column gives the area.
These numbers are equivalent to the
length and the width / breadth.
So the area of a rectangle can be written
as length x breadth or length x width.
Check this theory by drawing more rectangles:
Prisms draw 6
Spheres
5
Tetrahedra 4
but consider….
Q. If you double the length of a rectangle what
happens to its area?
Q. What would happen to the area if you
doubled the length and the width?
This is a patio.
Each paving slab measures 60cm by 60 cm.
Q. If we had used 30cm by 30 cm. paving slabs
would we have used twice as many?
We would have used 4 times as many because we
need 4 small slabs to cover each large one.
Q. How can we find the area of this shape?
4 cm
6 cm
A
B
4 cm
We can do it like this - by turning it into TWO shapes, inserting
the missing dimensions then adding the two areas A and B.
4 cm
4 cm
A
B
2 cm
or like this……
Use either method to work out the area of this shape then
draw a similar shape but with dimensions half the size.
Calculate the area of your new shape.
.
2 cm
4 cm
1 cm
6 cm
You should have something like this.
Its area should be 10
cm²
.
Using this shape repeat what you’ve just done.
You may need to make 3 areas this time.
By the end of the lesson the children should
be able to:
Express the formula for the area of a
rectangle first in words, then in
letters.
Choose a suitable unit to estimate the
area.
L.O.1
To be able to use doubling to multiply twodigit numbers by 4.
To halve any two-digit number.
We are going to double these numbers:
63
18
52
56
47
66
27
77
39
98
95
41
We are going to halve these numbers:
64
78
52
42
20
48
74
50
66
32
96
22
If we halve these numbers how can
we express the answers?
Will they be fractions or decimals?
23
87
65
93
31
47
59
75
19
24
Q. What is a quick way to multiply
this number by 4?
Doubling twice is the quick mental method to
multiply by four.
We’ll multiply each of these aloud by 4.
23
18
55
87
34
76
39
L.O.2
To be able to understand area measured
in square centimetres.
To understand and use the formula in
words “length x breadth” for
the area of a rectangle.
cm²
We used cm² to find the areas of shapes in yesterday’s lesson.
Here we have a square metre.
1metre
How many cm² are
there in I square
metre?
How can we work it
out?
1metre
1m²
1m² = 10 000cm²
because
and
and
length = 100cm.
breadth = 100cm.
100cm x 100cm = 10 000cm²
1mm²
Try to imagine a millimetre square
Q. How many mm² are there in 1cm²?
Q. How can we work it out?
1cm² = 100mm²
because
length = 10mm
and
breadth = 10mm
and 10cm x 10 cm = 100mm²
Which of the three units ( m² ,cm² , or mm²)
would be best for measuring these?
1.
2.
3.
4.
5.
6.
7.
The classroom floor.
An exercise book.
A postage stamp.
The playground.
A chocolate bar wrapper.
A mouse mat.
Your thumbnail.
.
2.8 cm
6.1 cm
The area of a rectangle is length x breadth or l x b for short.
Here the area would be 6.1 x 2.8 but it is useful first to get an
ESTIMATE
Q. What is the approximate area of the rectangle?
.
2.8 cm
6.1 cm
Rounding UP and DOWN leads to an approximate area of
6 x 3 = 18cm²
Let’s try with these:
1.
1.7cm
5.9 cm
Rounding UP and DOWN leads to
2.
6cm x 2 cm = 12cm²
3.2cm
11.8cm
Rounding UP and DOWN leads to 12cm x 3 cm = 36cm²
.
With a partner complete
Activity Sheet 7.1
. In which rectangles do you
think the area has been
underestimated?
Using calculators we’ll check
your estimates but will round
part-answers to the nearest
whole number.
Q. What areas of shapes in
the classroom would you
measure in mm², cm², or m²?
Record about a dozen
altogether.
In your book draw rectangles using cm and mm and
write their length and breadth. Be accurate!
Your partner must first estimate the area by rounding up
or down then work out the area to the nearest whole
number using a calculator.
Record both the estimate and the final answer.
Tetrahedra draw 2
Spheres draw 3
Prisms draw
4
Extension: measure area to two decimal points.
By the end of the lesson children should
be able to:
Express the formula for the area of a
rectangle first in words then in
letters.
Choose a suitable unit to estimate the
area.