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: www.ajtlearning.com
2 15 ,
2 45 ,
2 85
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. 35 3 * 4 = 12 2. Then simply put 25 after it. 12 25 So, 352 = 1225 www.ajtlearning.com
3
Square a two digit number ending in 5
Here is another example: Step-1: 95 9 * 10 = 90 Setp-2: 90 25 2 So, 95
= 9025
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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.
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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.
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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 xyz * 11 =
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x
y x+y
z y+z
z
11
Multiply any number by 11
Take the number 263 2
263 * 11 =
6
2
3
8
9
3
Lets try another number 485 4 263 * 11 = www.ajtlearning.com
5
8 1
3
5 1
3
5 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. 12 +14 16
2. Place a 0(zero) after it. 16 160 www.ajtlearning.com
14
Multiply two numbers between 10 and 20
3. Multiply the second digits of the two numbers. 14 *12 8
4. Add this number with the step-2 result. 160 + 8 168 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
Step-3:
7 * 3 = 21
Step-4:
200 + 21 = 221
200
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
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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. 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 divisible by 7. So, 3752 is also divisible by 7. You may have gone even further, 35
3 - 5*2
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-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: 8525 8-5+2-5=0 So, it is divisible by 11. Take: 392755 3 - 9 + 2 - 7 + 5 - 5 = -11 Also divisible by 11 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
It is divisible by 13. Lets try another: 754 754
75 + 4*4
75 + 16
91
9+1*4 13
So, you know. www.ajtlearning.com
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So we have leant a lot of math tricks today.
Practice to make them perfect for you. www.ajtlearning.com
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There is one math trick only for
YOU! www.ajtlearning.com
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Lets see if you can do it right!
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25
Add these numbers one after another1000 20
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26
Add these numbers one after another1000 20 1000 30
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Add these numbers one after another1000 20 1000 30 1000 40
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26
Add these numbers one after another1000 20 1000 30 1000 40 1000 10
26
Add these numbers one after another1000 20 1000 30 1000 40 1000 10 5000 ??? www.ajtlearning.com
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Add these numbers one after another1000 20 1000 30 1000 40 1000 10 5000 ??? www.ajtlearning.com
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. 26
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