Here are the 5 simple or easy math short tricks by mathematicsplus.com
1) Adding large numbers
Adding large numbers just in your head can be difficult. This method shows how to simplify this process by making all the numbers a multiple of 10. Here is an example:
644 + 238
While these numbers are hard to contend with, rounding them up will make them more manageable. So, 644 becomes 650 and 238 becomes 240.
Now, add 650 and 240 together. The total is 890. To find the answer to the original equation, it must be determined how much we added to the numbers to round them up.
650 – 644 = 6 and 240 – 238 = 2
Now, add 6 and 2 together for a total of 8
To find the answer to the original equation, 8 must be subtracted from the 890.
890 – 8 = 882
So the answer to 644 +238 is 882.
2) Division tricks
Here’s a quick way to know when a number can be evenly divided by these certain numbers:
- 10 if the number ends in 0
- 9 when the digits are added together and the total is evenly divisible by 9
- 8 if the last three digits are evenly divisible by 8 or are 000
- 6 if it is an even number and when the digits are added together the answer is evenly divisible by 3
- 5 if it ends in a 0 or 5
- 4 if it ends in 00 or a two digit number that is evenly divisible by 4
- 3 when the digits are added together and the result is evenly divisible by the number 3
- 2 if it ends in 0, 2, 4, 6, or 8
3) Cube Root
Follow the steps given below to quickly find out the cube root of a number.
Example: What is the cube root of 9261
Step 1: Find the numbers between 1 to 9 whose cube is equal to the digit present at the one’s place, here it is 1. So, we get 1×1×1 = 1
Step 2: See the first digit of the number, in this case, 9. 9 lies between the cube of 2 (2×2×2=8) and (3×3×3 = 27). Since 8 is closest to 9. Cube root of 9261 is 21.
Note: To find the cube root of 5 digit number, use the first two digits instead of first digit in step 2
Try one example by yourself to understand the trick even better:
Example: What is the cube root of 32768
Step 1: 23 = 8
Step 2: 33 = 27 and 43 = 64
Since, 27 is closer to 32, the cube root of 32768 will be 32.
4)SHORTCUT TRICK – 3 (Calculation of Multiple Interest on CI)
If a loan is taken for more than 1 year and the rate of interest in varying for different years, you can directly use the formula given here to calculate the answer.
Amount = P[1+R1/100] [1+R2/100] [1+R3/100] where R1 = rate of interest for 1st year, R2 for the second year and so on.
5). 10 and 11 times tricks
The trick to multiplying any number by 10 is to add a zero to the end of the number. For example, 62 x 10 = 620.
There is also an easy trick for multiplying any two-digit number by 11. Here it is:
11 x 25
Take the original two-digit number and put a space between the digits. In this example, that number is 25.
Now add those two numbers together and put the result in the center:
2_(2 + 5)_5
The answer to 11 x 25 is 275.
If the numbers in the center add up to a number with two digits, insert the second number and add 1 to the first one. Here is an example for the equation 11 x 88
(8 + 1)_6_8
There is the answer to 11 x 88: 968