Multiplication
Multiplication of numbers whose unit digit is 5 and the difference between both numbers is 10.
Eg. 25×35 (difference is 10)
2(3+1)|75
2×4 | 75
8| 75 = 875 Ans.
Trick :- 75 is compulsory.
We always add 1, in the greatest digit.
In the above example, we add 1 in 3 & after adding multiply by 2, get 8.
Eg. 55×65
5(6+1)|75
5×7|75
35|75 = 3575 Ans.
Trick 1 :- 75 is compulsory.
We always add 1, in the greatest digit.
In the above example, we add 1 in 6 & after adding multiply by 5.
Similarly, 105×115
10(11+1)|75
10×12|75
120|75 = 12075 Ans.
Do it themselves.
85×95
135×145
175×185
245×255
One more Eg. 135×125
12(13+1)|75
12×14|75
168|75 = 16875
Trick 2 :- Multiplication of two digits numbers both numbers have tens digit is 1 only.
Eg. 12×15 => 10 (2×5)
7 (2+5)
+ __1___ (common)
= 180 Ans.
Eg. 16×19 => 54 (6×9)
15 (6+9)
+ __1____ (comman)
= 1204 Ans.
Do it themselves.
15×18
16×14
13×15
16×17
Trick 3 :- Multiplication of two digits numbers both numbers have unit digit is 1 only.
Eg. 51×31 => 1 (comman)
8 (5+3)
+ __15____(5×3)
= 1581 Ans.
Eg. 61×81 => 1 (comman)
14 (6+8)
+__48____(6×8)
= 4941 Ans.
Do it themselves.
81×41
71×51
61×21
61×91
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