Page 117 - year book 22-23(22.08)

INTERESTING MATH TRICKS

Trick 1: Take Any Number and Multiply It by Three for a Cool Trick
Take any number, and multiply it by three. Then, take the digits of that new number and add them all
together. Whatever number that equals will always be divisible by three, no matter what number you
started with. For example:
ó 3X4 = 12

ó 1+2=3
ó 3/3=1
Trick 2: Multiplied By 15
ò Consider the multiplication of two numbers say 56 and 15
ò Now add zero at the end of the first number, it becomes 560.
ò Divide that number by 2; we get 560/2 = 280
ò Add the resultant number with 560, so 560 + 280 = 840.
ò So, the answer for 56 and 15 is 840.

Trick 3: Math's Trick to Find 5% of a number
Û Let us take; we have to find the percentage of the number 5% of 475, follow the steps.
Û For the given number, move the decimal point over by one place. 475 becomes 47.5
Û Then divide the number 47.5 by 2, we get 23.75.
Û 23.75 is the solution to the given problem.

Trick 4: Quickly square a two-digit number that ends in 5

« Let's use the number 35 as an example.
« Step 1: Multiply the first digit by itself plus 1.
« Step 2: Put a 25 at the end.
« 35 squared = [3 x (3 + 1)] & 25
« [3 x (3 + 1)] = 12
« 12 & 25 = 1225

Trick 5: The 11 rules
ß The 11 rule is one of those magic tricks and methods that can be used to quickly multiply two-digit

numbers by 11 in your head.
ß Separate the two digits in your mind. Add the two digits together.
ß Place the number from Step 2 between the two digits. If the number from Step 2 is greater than 9, put
the one's digit in the space and carry the ten's digit
ß For example: 72 x 11 = 792.
ß 57 x 11 = 5 _ 7, but 5 + 7 = 12, so put 2 in the space and add the 1 to the 5 to get 627.