Why Does The 9 Hand Trick Work?

What is the 9 trick in math?

A Mathemagical Trick Start by thinking of a number, any number.

Now, multiply that number by 9.

If the result is a multi-digit number, add its digits together to come up with a new number.

If that new number is still a multi-digit number, add its digits together to come up with yet another new number..

Is there a trick for multiplying by 8?

A Secret Trick When you need to multiply by 8, just double a number 3 times. To double a number means to multiply it by 2. This works because 2 x 2 x 2 = 8!

How does the 1089 trick work?

The mystery is this: first, take any three digit number, where the first and last digits differ by two or more and reverse the number to produce a new one. Then subtract the smaller from the larger producing another new number. If you reverse this number and this time add the two, the result will always be 1089.

What 2 Numbers add up to 9?

2 + 7 = 9, cross out 2 and 7. 2.4 + 3 = 9, cross out 4, 3 and 2. 3. There are no other groups of numbers adding up to 9.

Is your number 5 trick?

The Number 5 Trick Ask somebody to think of a number and keep it secret. … Example: 43 Add the next highest number to it 43 + 44 = 87 Add 9 87 + 9 = 96 Divide by 2 96 / 2 = 48 Subtract your original number 48 – 43 = 5 Everyone’s answer will always be 5 Try another number.

What is the trick to learning multiplication tables?

Tricks by Numberadd the number to itself (in other words, double it) Example 2×9 = 9+9 = 18.double, then double again. … Cut in half, then times 10. … when you multiply 6 by an even number, they both end in the same digit. … 7×8. … Double, double, double! … is 10× the number minus the number. … put a zero after it.More items…

Is there a trick for multiplying by 6?

There’s no special rule for multiplying by 6. You just have to remember this. When you multiply an even number by 6, the last digit of the answer is the same as the number that’s being multiplied. … 😺 Secret trick: think of multiplying by 6 as multiplying by 5 and adding one more of the same number.

What is the hand trick for multiplying by 9?

Step 1: Hold up all 10 of your fingers. Imagine they’re numbered 1 through 10, as you see in the picture. Step 2: Since you’re multiplying 9 x 7, you fold down the seventh finger, like this. Step 3: Count the number of fingers to the left of the folded finger (6).