Multiplication ppt
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Transcript of Multiplication ppt
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