To multiply any two digit number by 11:
For this example we will use 54.
Separate the two digits in you mind (5__4).
Notice the hole between them!
Add the 5 and the 4 together (5+4=9)
Put the resulting 9 in the hole 594. That's it! 11 x 54=594
The only thing tricky to remember is that if the result of the addition is greater than 9, you only put the "ones" digit in the hole and carry the "tens" digit from the addition. For example 11 x 57 ... 5__7 ... 5+7=12 ... put the 2 in the hole and add the 1 from the 12 to the 5 in to get 6 for a result of 627 ... 11 x 57 = 627
For this example we will use 54.
Separate the two digits in you mind (5__4).
Notice the hole between them!
Add the 5 and the 4 together (5+4=9)
Put the resulting 9 in the hole 594. That's it! 11 x 54=594
The only thing tricky to remember is that if the result of the addition is greater than 9, you only put the "ones" digit in the hole and carry the "tens" digit from the addition. For example 11 x 57 ... 5__7 ... 5+7=12 ... put the 2 in the hole and add the 1 from the 12 to the 5 in to get 6 for a result of 627 ... 11 x 57 = 627
For this example we will use 25
Take the "tens" part of the number (the 2 and add 1)=3
Multiply the original "tens" part of the number by the new number (2x3)
Take the result (2x3=6) and put 25 behind it. Result the answer 625.
Try a few more 75 squared ... = 7x8=56 ... put 25 behind it is 5625.55 squared = 5x6=30 ... put 25 behind it ... is 3025
Take the "tens" part of the number (the 2 and add 1)=3
Multiply the original "tens" part of the number by the new number (2x3)
Take the result (2x3=6) and put 25 behind it. Result the answer 625.
Try a few more 75 squared ... = 7x8=56 ... put 25 behind it is 5625.55 squared = 5x6=30 ... put 25 behind it ... is 3025
Recurring Number Magic
EffectYou write down the following 8 digit number on a piece of paper:
1 2 3 4 5 6 7 9
Then ask a friend to circle one of the digits. Say that they circle number 7.
You then ask your friend to multiply the 8 digit number by 63, and magically the result ends up being:
1 2 3 4 5 6 7 9 x
EffectYou write down the following 8 digit number on a piece of paper:
1 2 3 4 5 6 7 9
Then ask a friend to circle one of the digits. Say that they circle number 7.
You then ask your friend to multiply the 8 digit number by 63, and magically the result ends up being:
1 2 3 4 5 6 7 9 x
6 3
------------------
7 7 7 7 7 7 7 7 7
with the answer as a row of the chosen number 7.
The SecretWhen your friend circles a number, you need to multiply the chosen number by 9 in your head - if 3 was chosen you would work out 3 x 9 = 27. Then you need to ask your friend to multiply the 8 digit number by the number you have just worked out. In the case of 3 being chosen you ask your friend to multiply 12345679 by 27 and you magically get the answer 333333333.
