MULTIPLICATION

BY: ABHA ARORA

12 can be breaked as (10 + 2 )

Multiplication by breaking numbers

4 x 7

Break 7 as (5 + 2)

4 x 2 = 8 4 x 5 = 20

4 x 7 = 4 x (5 + 2) = 4 x 5 + 4 x2 = 20 + 8 = 28

Lets take one more example

12 x 2

10 x 2 = 20 2x 4 = 4

( 10 + 2 ) x 2 = 10 x 2 + 2x 2

= 20 + 4

= 24

Find the product by breaking up a factor

a) 37 x 8 = ? 37 = ( 30 + 7 ) 37 x 8 = (30 x 8) +

(7 x 8) = 240 + 56 = 296

B) 235 x 3 = ? 235 = 200 + 30

+ 5235 x 3 = (200 x 3) +

(30 x 3) + (5 x 3) = 600 + 90

+ 15 = 705

a) 146 x 8 146 = 100 + 40 + 6

146 x 8 = ( 100x8 ) + ( 40x8 ) + ( 6x8 )

= 800 + 320 +48

= 1168

Multiplying by doubling If we know the 2 times table then we can

work out the 4 times table by doubling. Example

8 x 2 = 16 then 8 x 4 = 32Here 4 is the double of 2 and 32 is the double of 16

Similar examples : If 1 x 8 = 8 then 1 x

16 = 16

2 x 8 = 16 then 2 x 16 = 32 3 x 8 = 24 then

3 x 16 = 48

ACTION TIME : Double the 6 times

table to find the product of :

A) 7 x 12 =? We know 7 x 6 = 42

, so 7 x 12 = ??

B) 3 x 12 = ?

3 x 6 = 18 , so 3 x 12 = ?

C) 8 x 12 = ?

8 x 6 = 48 , so 8 x 12 = 96

Using multiples of 10 to multiply other numbers

8 x 19 = ? 8 x 20 =160 -

8 1 5 2

6 x 39 = ?

6 x 40 = 240 - 6

234

Use multiples of 10 to find these products : A) 8 x 29

30 is nearest tens to 29 , so we will find the

8 x 30 = 240 - 8

232

B) 9 x 49 = ?

9 x 50 = 4 5 0 - 9 4 4 1

C) 4 x 69 = ?

4 x 70 = 2 8 0 - 7

2 7 3