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Learn Mathematics TRICKS From AJT Learning.com www.ajtlearning.com
Today we will learn some cool math tricks. So that, we can use more our brain and less our calculator. www.ajtlearning.com 1
Square a two digit number ending in 5 For example: 152, 452, 852 www.ajtlearning.com 2
Square a two digit number ending in 5 Lets consider the number 35. 1. We take the first digit and multiply it with it’s next number. 3 5 3 * 4 = 12 2. Then simply put 25 after it. 1 2 2 5 So, 352 = 1225 www.ajtlearning.com 3
Square a two digit number ending in 5 Here is another example: Step-1: 9 5 9 * 10 = 90 Setp-2: 9 0 2 5 So, 952= 9025 www.ajtlearning.com 4
Multiply any number by 4 Simply double the number two times. www.ajtlearning.com 5
Multiply any number by 4 Take the number 63 63*4 = 63*(2*2) = (63*2)*2 = 126*2 = 252 Lets try another number 753 double of 753 = 1506 double of 1506 = 3012 So, 753 * 4 = 3012 www.ajtlearning.com 6
Multiply any number by 5 Simply half the number & multiply it by 10. www.ajtlearning.com 7
Multiply any number by 5 Take the number 86 86*5 = 86*(10/2) = (86/2)*10 = 43*10 = 430 Lets try another number 495 half of 495 = 247.5 247.5 * 10 = 2475 So, 495 * 4 = 2475 www.ajtlearning.com 8
Multiply any number by 15 Multiplication by 10 + Multiplication by 5. www.ajtlearning.com 9
Multiply any number by 15 Take the number 84 84*10 = 840 84*5 = (84/2)*10 = 42*10 = 420 84*15 = 840 + 420 = 1260 Lets try another number 495 495*15 = 495*10 + 495*5 = 4950 + (495/2) * 10 = 4950 + 2475 = 7425 www.ajtlearning.com 10
Multiply any number by 11 x y z xyz * 11 = x x + y y + z z www.ajtlearning.com 11
Multiply any number by 11 Take the number 263 2 6 3 263 * 11 = 2 8 9 3 Lets try another number 485 4 8 5 263 * 11 = 5 3 3 5 1 1 www.ajtlearning.com 12
Multiply two numbers between 10 and 20 For example: 15*17, 19*13 www.ajtlearning.com 13
Multiply two numbers between 10 and 20 Lets consider the number 12*14. 1. Add the first number with the other number’s second digit. 1 2 + 1 4 1 6 2. Place a 0(zero) after it. 1 6 1 6 0 www.ajtlearning.com 14
Multiply two numbers between 10 and 20 3. 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 + 1 6 8 8 So, 12*14 = 168 www.ajtlearning.com 15
Multiply two numbers between 10 and 20 Here 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 www.ajtlearning.com 16
Divisibility Check For example: is 7403 is divisible by 11 ? www.ajtlearning.com 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. www.ajtlearning.com 18
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. 91 9 1 9 - (1*2) 7 Now, if the number is 0 or divisible by 7, then the original number is also divisible by 7. www.ajtlearning.com 19
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 divisibleby 7. So, 3752 is also divisibleby 7. Youmayhavegoneevenfurther, 35 3-5*2 -7 ; whichisalsodivisibleby7. www.ajtlearning.com 20
Divisibility Check (for 11) For 11, add and subtract digits in an alternative pattern (like- 1stdigit - 2nddigit + 3rddigit …). Take:8525 8-5+2-5=0 So,itisdivisibleby11. Take:392755 3-9+2-7+5-5=-11 Alsodivisibleby11 www.ajtlearning.com 21
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 Itisdivisibleby13. Letstryanother:754 754 75+4*4 75+16 91 9+1*4 13 So, you know. www.ajtlearning.com 22
So we have leant a lot of math tricks today. Practice to make them perfect for you. www.ajtlearning.com 23
There is one math trick only for YOU! www.ajtlearning.com 24
Lets see if you can do it right! www.ajtlearning.com 25
Add these numbers one after another- 1000 20 www.ajtlearning.com 26
Add these numbers one after another- 1000 20 1000 30 www.ajtlearning.com 26
Add these numbers one after another- 1000 20 1000 30 1000 40 www.ajtlearning.com 26
Add these numbers one after another- 1000 20 1000 30 1000 40 1000 10 26
Add these numbers one after another- 1000 20 1000 30 1000 40 1000 10 5000 ??? www.ajtlearning.com 26
Add these numbers one after another- 1000 20 1000 30 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. 1000 40 1000 10 5000 ??? www.ajtlearning.com 26