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Slide 1

Welcome to the World of MATHEMA-TRICKS

Minhas Kamal

Today we will learn some cool math tricks.So that, we can use more our brain and less our calculator.1

Square a two digit number ending in 5For example: 152, 452, 852 2

Square a two digit number ending in 5Lets consider the number 35.1. We take the first digit and multiply it with its nextnumber.3 5 3 * 4 = 12

2. Then simply put 25 after it.1 2 2 5

So, 352 = 12253

Square a two digit number ending in 5Here is another example:Step-1:9 5 9 * 10 = 90Setp-2:

9 0 2 5So, 952 = 9025

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Multiply any number by 4Simply double the number two times.5

Multiply any number by 4Take the number 6363*4 = 63*(2*2) = (63*2)*2 = 126*2 = 252

Lets try another number 753double of 753 = 1506double of 1506 = 3012So, 753 * 4 = 30126

Multiply any number by 5Simply half the number &multiply it by 10.7

Multiply any number by 5Take the number 8686*5 = 86*(10/2) = (86/2)*10 = 43*10 = 430

Lets try another number 495half of 495 = 247.5247.5 * 10 = 2475So, 495 * 4 = 24758

Multiply any number by 15Multiplication by 10 + Multiplication by 5.9

Multiply any number by 15Take the number 8484*10 = 84084*5 = (84/2)*10 = 42*10 = 42084*15 = 840 + 420 = 1260

Lets try another number 495495*15 = 495*10 + 495*5 = 4950 + (495/2) * 10 = 4950 + 2475 = 7425

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Multiply any number by 11xyzxy + zzx + yxyz * 11=11

Multiply any number by 11Take the number 263Lets try another number 485

2632938263 * 11=4855353263 * 11=1112

Multiply two numbers between 10 and 20For example: 15*17, 19*13 13

Multiply two numbers between 10 and 20Lets consider the number 12*14.1. Add the first number with the other numberssecond digit.1 2 + 1 41 6

2. Place a 0(zero) after it.1 6 1 6 0

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Multiply two numbers between 10 and 203. Multiply the second digits of the two numbers.1 4 * 1 2 8

4. Add this number with the step-2 result.1 6 0 + 81 6 8

So, 12*14 = 16815

Multiply two numbers between 10 and 20Here is another example: 17*13 Step-1:17 + 3 = 20 Setp-2:20 200 Step-3:7 * 3 = 21 Step-4:200 + 21 = 221

So, 17*13 = 221

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Divisibility CheckFor example: is 7403 is divisible by 11 ?17

Divisibility Check (for 2, 3)A number is divisible by 2 if its last digit is 0, 2, 4, 6 or 8. For example: 12, 5394, 993120. A number is divisible by 3 if sum of its digits is divisible by 3. For example: 72 is divisible by 3 as 7+2=9 which is divisible by 3.Another example: 57381, 5+7+3+8+1=24; 24 is divisible by 3. So 57381 is also divisible by 3.

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Divisibility Check (for 5, 7)A number is divisible by 5 if its last digit is 0 or 5. For example: 100, 3795, 698170. For 7, separate & double the last digit of the number. Then subtract it from the rest. Take: 91. 919 19 - (1*2) 7 Now, if the number is 0 or divisible by 7, then the original number is also divisible by 7.

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Divisibility Check (for 7)If the number is big then continue the process as many time as needed. Lets take 3752.3752 375 2*2 371 37 1*2 35 Now, 35 is divisible by 7. So, 3752 is also divisible by 7.You may have gone even further, 35 3 - 5*2 -7 ; which is also divisible by 7.20

Divisibility Check (for 11)For 11, add and subtract digits in an alternative pattern (like- 1st digit - 2nd digit + 3rd digit ).Take: 85258 - 5 + 2 - 5 = 0So, it is divisible by 11. Take: 3927553 - 9 + 2 - 7 + 5 - 5 = -11Also divisible by 11

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Divisibility Check (for 13)For 13, add 4 times of the last digit to the rest of the number. Take: 351 351 35+1*4 39 It is divisible by 13.Lets try another: 754 754 75 + 4*4 75 + 16 91 9+1*4 13 So, you know.

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So we have leant a lot of math tricks today.Practice to make them perfect for you.23

There is one math trick only for YOU!24

Lets see if you can do it right!25

Add these numbers one after another- 1000 2026

Add these numbers one after another- 1000 201000 3026

Add these numbers one after another- 1000 201000 301000 4026

Add these numbers one after another- 1000 201000 301000 401000 10

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Add these numbers one after another- 1000 201000 301000 401000 105000 ???

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Add these numbers one after another- 1000 201000 301000 401000 105000 ???

If your answer is 5000, then you are among the most who mistook. The actual answer is 4100. Count again and see if you get it right this time.

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