Date post: | 18-Jan-2016 |
Category: |
Documents |
Upload: | cornelius-walker |
View: | 224 times |
Download: | 4 times |
© Boardworks Ltd 2004 1 of 56
Calculating with fractions
Fraction Mathematics in Primary Schools
© Boardworks Ltd 2004 2 of 56
A1
Contents
Calculating with fractions
Multiplying fractions
© Boardworks Ltd 2004 3 of 56
Multiplying fractions by integers
We can illustrate this calculation on a number line:
0
14
14
14
12
14
34
14
1
14
141
14
121
14
341
14
2
14
What is 8 × ?
© Boardworks Ltd 2004 4 of 56
Again, we can illustrate this calculation on a number line:
0
34
34
34
121
34
142
34
3
34
343
34
124
34
145
34
6
34
346
34
127
34
148
34
9
34
What is 12 × ?
Multiplying fractions by integers
© Boardworks Ltd 2004 5 of 56
Let’s use a number line again:
0
13
13
13
23
13
1
13
131
13
231
13
2
13
132
13
232
13
3
13
What is 9 × ?
Multiplying fractions by integers
© Boardworks Ltd 2004 6 of 56
So,
8 × = 214
12 × = 934
9 × = 313
What do you notice?
What do you notice?
and
Multiplying fractions by integers
© Boardworks Ltd 2004 7 of 56
Following the rules of arithmetic, we know that,
8 ×14
=14
× 8
In maths the word ‘of’ (এর) means ‘times’ (গুণ).
=14
of 8 = 8 ÷ 4
These are equivalent calculations.
Multiplying fractions by integers
© Boardworks Ltd 2004 8 of 56
Means the same as:
35
20 ×
35
× 2035
of 2015
3 × of 20
20 × 3 ÷ 5 20 ÷ 5 × 3 3 ÷ 5 × 20
Equivalent calculations
© Boardworks Ltd 2004 9 of 56
When we multiply a fraction by an integer we:
multiply by the numerator
and
divide by the denominator
For example,
49
54 × = 54 ÷ 9 × 4
= 6 × 4
= 24
Multiplying fractions by integers
© Boardworks Ltd 2004 10 of 56
When we multiply by a fraction we:
multiply by the numerator
and
divide by the denominator
Multiplying fractions
© Boardworks Ltd 2004 11 of 56
Exercise A Work out the following
1) 2 1 2) 2 4 3) 6 2 4 3 5
4) 2 10 5) 4 7 6) 3 123 9 5
© Boardworks Ltd 2004 12 of 56
Counting on and back using fractions
© Boardworks Ltd 2004 13 of 56
Presentation By
MD SABBIR HOSSAIN (010-066)
© Boardworks Ltd 2004 14 of 56
Thank you all.