The 11 rule for 2 digit number:
All of you know the simple rule of multiplying a number with 10 or 10^x. Now I am going to tell you the rule for multiplication by 11.
I am using 34 for example purpose
1. Separate the two digit 3__4
2. Add the digits 3+4=7
3. Put that 7 in the gap of 3__4.
4. The number becomes 374.
5. Now 11*34=374
Note: If the sum of the digits is > than 9. Then take the digit in the unit's place and put it into the hole and take the digit in the ten's place and add it to the digit in ten's place of the original number.
For example: 75
1. 7__5
2. 7+4=12
3. (7+1) 2 _5
4. 74*11=825
Square a two digit number:
I am using 72 for example
1. Look for the nearest 10 boundary. In this case it is 70.
2. So the distance from 72 is 2 down.
3. Now go 2 up from 72, i.e. 74
4. Multiply 70 and 74. It would be easy if you take it as 74*10*7=5180
5. Now square the distance i.e. 2*2=4
6. Add it to 5180, i.e. 5180+4=5184
7. Now 72*72=5184
More tips and tricks soon.
All of you know the simple rule of multiplying a number with 10 or 10^x. Now I am going to tell you the rule for multiplication by 11.
I am using 34 for example purpose
1. Separate the two digit 3__4
2. Add the digits 3+4=7
3. Put that 7 in the gap of 3__4.
4. The number becomes 374.
5. Now 11*34=374
Note: If the sum of the digits is > than 9. Then take the digit in the unit's place and put it into the hole and take the digit in the ten's place and add it to the digit in ten's place of the original number.
For example: 75
1. 7__5
2. 7+4=12
3. (7+1) 2 _5
4. 74*11=825
Square a two digit number:
I am using 72 for example
1. Look for the nearest 10 boundary. In this case it is 70.
2. So the distance from 72 is 2 down.
3. Now go 2 up from 72, i.e. 74
4. Multiply 70 and 74. It would be easy if you take it as 74*10*7=5180
5. Now square the distance i.e. 2*2=4
6. Add it to 5180, i.e. 5180+4=5184
7. Now 72*72=5184
More tips and tricks soon.
