Mathematics is seen as the realm of logic and rationality, It has been identified as the hardest academic field of learning. Students usually tremble during Mathematics examinations and usually, students fail this subject or course out of ignorance especially when calculators are not allowed.

Even so(realm of logic and rationality), there is a lot of trickiness in the number world! From quick ways to do arithmetic to various statistical anomalies.

Make sure you double check with different digits to learn these tricks.

MULTIPLYING BY 5–

To do this quickly, divide by 2 and multiply by 10.
Example 14*5 is 14/2=7, 7*10 = 70

MULTIPLYING BY 4–

This seems obvious but to do this in your head, just double the number twice.
Example 30*4 is 30+30=60, 60+60=120.

MULTIPLYING BY 3–

Check if a number is a multiple of 3 simply by checking whether the sum of its digits is a multiple of 3.

ALL THE SQUARES–

You can get every square number by adding up the odd numbers.
Here is a start: 1=1*1, 1+3=4,2*2, 1+3+5=9,3*3, 1+3+5+7=16, 4*4

MULTIPLYING BY 1001-  

Any three digit number multiplied by 1001 will give that number twice. 456*1001 is 456,456.

PERCENTAGE TRICK–

x% of Y= Y% of x, 50% of 20 is 20% of 50

50% of $100 is $15, so then 15% of 50 is half of that, or $7.50. Also, you know that 15% of $10 is $1.50.

ADDING 5–

This seems counterintuitive but what you are about finding out is mind blowing. It has been shown that people can add 5 to any number greater than 5 if they subtract 5 and then add 10,they arrive at the answer.
Example:9+5 is 9-5=4, 4+10=14

Subtracting a large number from 1000.

To subtract a large number from 1000 you can use this basic rule: subtract all but the last number from 9 (taking the absolute value… that is, ignoring if the number is negative), then subtract the last number from 10:

1000
– 736

Step 1: subtract 7 from 9 = 2
Step 2: subtract 3 from 9 = 6
Step 3: subtract 6 from 10 = 4

Your answer: 264

MULTIPLYING BY 11–

To multiply a 2 digit number by 11, just take the sum of its digits, place it as a single digit number just right in between the digits. If it is greater than 2 digits, carry the 1 and add it to the first digit.
Example: 34*11=374     also    47*11=517 (carried 1 which became 5)

MULTIPLYING BY 9–

To make this arithmetic easier, simply multiply the number by 10 and subtract the other number(multiplied).
Example: 23*9=230,230-23=207.

MULTIPLYING BY 13-

If it is a 2 digit number, Take 3 from the 13, add it to the digit, multiply by 10. Then, multiply the last digit of the multiplied and the multiplier, finally sum up the result of the two calculations.

Example 17*13 is 17 +3=20, 20*10=200. 7*3=21. Therefore 200+21=221
MULTIPLYING BY 6:

Multiply the number by 3 first and multiply again by 2.

Example: 7*6 is 7*3=21, 21*2=42
MULTIPLYING BY 12:

Multiply the digits by 10 and add twice the original number

Example: 14*12 is 14*10=140, 140+14+14(28)=168
MULTIPLYING BY 13:

Multiply by 3 and add 10 times original number.

Example 18*13 is 18*3=54, 18*10=180. therefore 180+54=234

MULTIPLYING BY 14:

Multiply by 7 and then multiply by 2

Example 19*14 is 19*7=133, 133*2=266

MULTIPLYING by 15:

Multiply by 10 and add 5 times the original number

Example 13*15 is 13*10=130, 13*5=65. therefore 130+65=195.

TRY THESE TRICKS YOURSELF BY CHOOSING A CERTAIN NUMBER OF YOUR CHOICE.

You can use the comment box to record your findings. Goodluck.

Multiplying by 16:
You can double four times or multiply by 8 and then by 2

Multiplying by 17:
Multiply by 7 and add 10 times original number

Multiplying by 18:
Multiply by 20 and subtract twice the original number

Multiplying by 19:
Multiply by 20 and subtract the original number

Multiplying by 24:
Multiply by 8 and then multiply by 3

Multiplying by 27:
Multiply by 30 and subtract 3 times the original number

Multiplying by 45:
Multiply by 50 and subtract 5 times the original number

Multiplying by 90:
Multiply by 9 and put a zero on the right

Multiplying by 98:
Multiply by 100 and subtract twice the original number

Multiplying by 99:
Multiply by 100 and subtract the original number

Start applying these tricks to save time spent in solving mathematical problems especially when the use of calculator in an examination is prohibited.

List of Project topics in Mathematics and statistics:

1). Time Series Analysis On Patient Attendance (a Case Study Of General Hospital Kofar Gayan, Zaria)

2). Statistical Analysis Of The Federal Government’s Expenditure And Revenue

For more fields, kindly check HERE

credits: SAMEEN IMTIAZ, 

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