Two digit multiplication in 3 seconds

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How to do multiplication from 10 x 10 to 20 x 20.

Try to do following examples and note the time to get the answer.

Ex 1 : 14 x 11 = ?
Ex 2 : 16 x 12 = ?
Ex 3 : 18 x 13 = ?

Now lets try using the trick. First let me explain the trick.

Ex 1 : 14 x 11 = ?

This is multiplication with 11. Did you remeber the trick which was discussed in previous post?

1's digit   : 4
10's digit :  1 + 4 = 5
100'digit :  1

So the answer is  154.

Now I am going to explain trick which is useful for multiplication from  10 x 10 to 20 x 20.

Ex 1 : 14 x 11

Instead of explaining the trick by me, just watch the video

Now you try multiplying the same numbers again and note the time.

Just an improvement to the method mentioned in the video.

Ex 2 : 16 x 12 = ?
       
1's digit : 6 x 2 = 12
10's digit : 16 + 2 = 18

So answer is 192 ( 1 in 12 carry forward to 10's digit )

Ex 3 : 18 x 13 = ?

1's digit : 8 x 3 = 24
10'digit : 18 + 3 = 21

So answer is 234 ( 2 in 24 carry forward to 10's digit )