When you see calculations, do you still use your calculators? This can help you in solving it quickly using only your head.
Mental calculations could be difficult if you don’t know how to solve. You tend to solve it using the calculator instead. Just try to solve mentally by just using these tricks.
Learning techniques on how to do mental calculations quickly can help you develop greater confidence in mathematics, improve mathematical skills and understanding, and excel in advanced courses. Here are some tricks on mental calculations that can help you.
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: 375 + 243 = ?
STEP ONE: Round off the numbers to the nearest tens so that you can solve it easily. In this step, you don’t need to consider the rule of rounding off numbers. Based on the example, 375 will become 380 and 243 will become 250.
STEP TWO: You need to determine how much you added to the numbers to round them up. Based on the example, 380 – 375 = 5; 250 – 243 = 7.
STEP THREE: Add the rounded numbers. Based on the example, 380 + 250 = 630.
STEP FOUR: Add the results in Step 2. Based on the example, 5 + 7 = 12.
STEP FIVE: Subtract the results of Steps 3 and 4. Based on the example, 630 -12 = 618.
Therefore, 375 + 243 = 618.
Subtracting from 100, 1000, 10000, 10n
The basic rule of subtracting numbers is that you need to subtract every number except the last from 9 and subtract the final number from 10
100 – 32 = _ _; 9 – 3 = 6 | 10 – 2 = 8 | 100 – 32 = 68.
1,000 – 164 = _ _ _; 9 – 1 = 8 | 9 – 6 = 3 | 10 – 4 = 6 | 1,000 – 164 = 836
10,000 – 96 = _ _ _ _; 9 – 0 = 9 | 9 – 0 = 9 | 9 – 9 = 0 | 10 – 6 = 4 | 10,000 – 96 = 9904
Multiplying 5 times any number
When multiplying the number 5 by any number, you can follow this method. For instance, 5 X 7
STEP ONE: Take the number being multiplied by 5 and cut it in half. Based on the example, 7 / 2 = 3.5
STEP TWO: Multiply the results of Step 1 by 10. Based on the example, 3.5 X 10 = 35.
Therefore, 5 x 7 = 35.
Multiplying by 10
The easiest way to multiply numbers by 10 is that you only add zero (0) at the end of any number. For instance, 12 X 10 = 120
Multiplying by 11
In multiplying numbers by 11, just follow these steps. For instance, 34 X 11.
STEP ONE: Take the original two-digit number and put a space between the digits. Based on the example, 3 _ 4.
STEP TWO: Add those two numbers together and put the result in the center. Based on the example, 3 + 4 = 7; 3 7 4.
Therefore, 34 X 11 = 374.
Quickly square a two-digit number that ends in 5
In squaring a two-digit number, just follow these steps. For instance, 65.
STEP ONE: Multiply the first digit by itself plus 1. Based on the example, 6 (6+1) = 6 (7) = 42
STEP TWO: Put a 25 at the end.
Therefore, the square of 65 is 4,225.
Tough multiplication
When multiplying large numbers, you will use this method will solve the problem quickly. For instance, consider 20 x 50 as an example.
STEP ONE: Divide the first number in half and multiply the second number twice. Based on the example, 20 / 2 = 10; 50 x 2 = 100.
STEP TWO: Multiply those answers together. Based on the example, 10 x 100 = 1,000.
Therefore, 20 X 50 = 1,000.
Multiplying numbers that end in zero
Here is the quickest way of multiplying numbers that end in zero. Consider 200 X 80 as an example.
STEP ONE: Multiply the non-zeros first. Based on the example, 8 x 2 = 16
STEP TWO: Count all zeros in the equation and add it at the end of your answer in Step 1. Based on the example, the equation has three zeros; making it 16,000.
Therefore, 200 X 80 = 16,000.
By learning these tricks, you would be able to accurately and confidently do mental calculations and solve mathematical problems that you once feared solving. According to the Room 241, “practicing these fast math tricks can help both students and teachers improve their math skills and become secure in their knowledge of mathematics—and unafraid to work with numbers in the future.“
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