How To Do Mental Math Fast

Mental math is the capability to do calculations in your head.Students can apply it to addition, subtraction, multiplication, and division.

Mental math relates to number sense – the ability to manipulate numbers in one’s head in various ways to do calculations.

Studies and research have proved number sense as a predictor of success for Mathematic students.

People with number sense can take apart and put together numbers in various ways to calculate proportions. It’s similar to words being deconstructed and reassembled to find humor or a story.

Or, if you learned how music is constructed, notes played on an instrument are reordered to make beautiful sounds and not just noise.

Mental math/number sense isn’t just for bright students—all learners can gain a considerable benefit.

Students learn the basics of these skills in elementary school, and it makes higher-level math much easier!

Kids are expected to know many English words as they grow up, so why not expect them to do the same with numbers?

Children need to learn how to mentally do calculations because the steadier they get at it, the easier it will be when tackling more complex mathematics, such as Mymathlab Answers!

Tricks For Doing Mental Math Fast

Here are a few ways that your young students can do math in their heads. Once these strategies are mastered, they should be able to accurately and confidently solve math problems they used to fear solving.

Mental Math Trick #1: Adding Large Numbers

Adding large numbers together can be tricky in your head. But this technique makes it simpler by using large and multiples of 10. Here is an example:

544 + 138

These numbers are hard to work with, but rounding them up will make them much more manageable. So, 544 becomes 550, and 138 becomes 140.

Now, add 550 and 140 together. The total is 690. Let’s find the answer to the original equation by determining how much we added to round up two of the numbers.

550 – 544 = 6 and 140 – 138 = 2

Now, add 6 and 2, you get a total of 8

To find the solution to the original problem, you must subtract 8 from the 690.

690 – 8 = 682

So the answer to 544 +138 is 882.

Mental Math Trick #2: Subtracting From A Large Number

Here’s a basic rule to subtract large numbers such as 1,000: Subtract the digits in multiples of ten until you reach 0. The final zero is subtracted from 10

For example:

1,000 – 446

Step 1: Subtract 4 from 9 = 5

Step 2: Subtract 4 from 9 = 5

Step 3: Subtract 6 from 10 = 4

The solution to the equation is 554.

Mental Math Trick #3: Multiplying 5 By An Even Number

For multiplying 5 by an even number, there is a quick way to find the answer.

For instance, 5 x 6

  • Step 1: Take the digit being multiplied by 5 and divide it in half. This makes the number 6 become the number 3.
  • Step 2: Add a zero to the digit to find the solution. In this case, the answer is 30.

5 x 6 = 30

When multiplying an odd number by 5, the formula is different.

For example, consider 5 x 5.

  • Step 1: Subtract one from the digit being multiplied by 5. In this instance, the number 5 becomes the number 4.
  • Step 2: Now halve the number 4, which makes it the number 2. Make 5 the last digit. The number produced is 25, which is the answer.

5 x 5 = 25

Mental Math Trick #4: Division

Here’s a way to tell when a number can be divided by specific numbers.

  • Ten: If the last digit of the number is a zero.
  • Nine: when the digits are added, and it is divisible by 9
  • Eight: if the last three digits are evenly divisible by 8 or are 000
  • Six: if it’s an even number, and when the digits are added together, the answer is evenly divisible by 3
  • Five: if it ends in a 0 or 5
  • Four: if it ends in 00 or a two-digit number that is evenly divisible by 4
  • Three: when the digits are added, and the result is divisible by the number 3
  • Two: if it ends in 0, 2, 4, 6, or 8

Mental Math Trick #5: Multiplication by 9

Here is a simple way of multiplying any number by nine. Ready?

Let’s use the example of 9 x 4.

Step 1: Subtract 1 from the digit that is being multiplied by 9.

4 – 1 = 3

The number 3 is the first number in the answer.

Step 2: Subtract that digit from the number 9.

9 – 3 = 6

The number6 is the second number of the answer to the equation.

So the solution, 9 x 4= 36

Mental Math Trick #6: The 10 & 11 Times Trick

To multiply any digit by the number 10, add a zero to the end of the number. For example, 52 x 10 = 520.

There is also an easy multiplication shortcut for any two-digit number by 11. Here it is:

11 x 35

If you have a two-digit number, put a space and then continue with the same digits. So in this example, that number is 35.


Now add both those numbers, and put the result in the middle:

3_(3 + 5)_5


The answer to 11 x 35 is 385.

If the number in the center adds up to a number with two digits, break it down into two numbers and add 1. Here is an example for the problem 11 x 77

7_(7 +7)_7

(7 + 1)_4_7


The answer to 11 x 77 is 847.

Mental Math Trick #7: Percentage

Finding the percentage of a number can be tricky, but with the correct understanding, it is effortless.

For example, to figure what 5% of 135 is, follow this process:

  • Step 1: Move the decimal point by one place. 135 becomes 13.5.
  • Step 2: Divide 13.5 by the number 2. The answer is 6.75. It is also the answer to the original problem.

Mental Math Trick #8: Squaring Two-Digit Number That Ends With 5

Let’s use the number 25 as an example.

  • Step 1: Multiplying the first number by itself and adding 1.
  • Step 2: Put 25 at the end.

25 squared = [2 x (2 + 1)] & 25

[2 x (2 + 1)] = 6

6 & 25 = 625

25 squared = 625

Mental Math Trick #9: Solving Tough Multiplication

For significant multiplication problems, divide the first number by two and double the second number.

Let’s Consider,

10 x 140

Step 1: Divide the 10 by 2, which equals 5—double 140, which equals 280.

Step 2: Now multiply the two answers.

5x 280 = 1400

The answer to 10 x 140 is 1,400.

Practicing these fast math tricks can help both students improve their math skills.

However, it is worthy of mentioning that most students, today, do not have the time to finish their homework on time, much less learn Mental Math.

In these circumstances, students can take advantage of take my online class services such as buyonlinceclass.com to have their work taken care of to focus on mastering this Mental math.


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