0 1
10
Multiply by 6
If you multiply 6 by an even number, the answer will end with the same number. Ten digits will be half of one digit.
Example: 6 x 4 = 24.
02
10
The answer is 2.
Think of a number.
Multiply by 3.
Add 6.
Divide this number by 3.
Subtract the number of step 1 from the answer in step 4.
The answer is 2.
03
10
The same three digits
Think of any three digits, each of which is the same. Such as 333, 666, 777 and 999.
Add up these figures.
Divide the answer in the second step by three digits.
The answer is 37.
04
10
Six digits become three digits.
Take any three-digit number and write it twice to form a six-digit number. For example, 37 137 1 or 552552.
Divide this number by 7.
Divided by 1 1.
Divided by 13.
The order in which you divide it doesn't matter!
The answer is three digits.
Example: 37 137 1 provides you with 37 1 or 552552 provides you with 552.
A related technique is to take any three numbers.
Multiply by 7, 1 1 and 13.
The result will be a six-digit number that repeats three digits.
Example: 456 becomes 456456.
05
10
1 1 rule
This is a quick way to multiply two digits by 1 1 in your mind.
Separate the two numbers in your mind.
Add up these two figures.
Put the number in step 2 between two digits. If the number in step 2 is greater than 9, fill in one digit in the blank and then fill in ten digits.
For example: 72 x 1 1 = 792.
57 x 1 1 = 5 _ 7, but 5+7 = 12, so put 2 in the space and add 1 and 5 to get 627.
06
10
Memory Pi
To remember the first seven digits of pi, please count the letters of each word in the sentence:
"How I wish I could calculate pi."
This becomes 3. 14 1592.
07
10
Contains the numbers 1, 2, 4, 5, 7, 8.
Select a number from 1 to 6.
Multiply this number by 9.
Multiply by 1 1 1.
Multiply by 100 1.
Divide the answer by 7.
This number will include the numbers 1, 2, 4, 5, 7 and 8.
For example, the number 6 gives the answer 7 14285.
08
10
Multiply large numbers in your mind.
To multiply two digits easily, use the distance between them and 100 to simplify the mathematical operation:
Subtract each number from 100.
Add these values together.
100 minus this number is the first part of the answer.
Multiply the number in step 65438 by +0 to get the second part of the answer.
09
10
Supersimple separable rule
You have 2 10 pizza, and you want to know if you can share it equally in your group. Instead of taking out your calculator, use these simple shortcuts to do the math in your mind:
If the last digit is a multiple of 2 (2 10), it can be divisible by 2.
If the sum of numbers is divisible by 3, it can be divisible by 3 (522, because numbers add up to 9 and can be divisible by 3).
If the last two digits are divisible by 4, they can be divisible by 4 (2540, because 40 can be divisible by 4).
If the last digit is 0 or 5 (9905), it can be divisible by 5.
If it satisfies the rules of both 2 and 3, it can be divisible by 6 (408).
If the sum of numbers is divisible by 9, it can be divisible by 9 (6390, because 6+3+9+0 = 18, it can be divisible by 9).
If the number ends with 0 (89 10), it can be divisible by 10.
If the rule divisible by 3 and 4 is applicable, it can be divisible by 12.
Example: 2 10 slices of pizza can be divided into 2, 3, 5, 6 and 10 groups on average.
10
10
Finger multiplication table
Everyone knows that you can count with your fingers. Do you know that you can use them for multiplication? There is a simple way to make the multiplication table of "9", that is, put your hand in front of you and extend your finger and thumb. To multiply a number by 9, please fold the digital finger down and count from the left.
For example, to multiply 9 by 5, please fold the fifth finger down from the left. Count the fingers on both sides of the fold and get the answer. In this case, the answer is 45.
Multiply 9 by 6 and fold the ring finger down. The answer is 54.