PSC MODEL QUESTION - 19

In this tutorial we will try to learn a simple but effective shortcut technique for multiplying any number with 11 without using a pen or pencil or evening writing on paper.

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Lets first start with any no. multiplied by 11.

3152 x 11 = ?

The first digit and last digit of the answer will remain constant 3 and 2.

Just keep adding the consecutive No.s

∴ 3152 x 11 = 34672

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Some Examples

Example:1
53241 x 11 = ?
First Digit 5 as it is 
5+3 = 8
3+2 = 5
2+4 = 6
4+1 = 5
Last Digit 1 as it is
∴ 53241 x 11 = 585651

Example:2
26134 x 11 = ?
First Digit 2 as it is 
2+6 = 8
6+1 = 7
1+3 = 4
3+4 = 7
Last Digit 4 as it is
∴ 26134 x 11 = 287474

Example:3
23586 x 11 = ?
First Digit 2 as it is 
5+3 = 5
3+2 = 8
2+4 = 13
4+1 = 14
Last Digit 6 as it is
Now apply balancing rule
∴ 23586 x 11 = 259446

Example:4
38429 x 11 = ?
First Digit 3 as it is 
2+6 = 11
6+1 = 12
1+3 = 6
3+4 = 11
Last Digit 9 as it is
Now apply balancing rule
∴ 38429 x 11 = 422719

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Let try this trick on a bigger number : -

6274598712 x 11 = ?

6274598712 x 11 = 69020585832