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Mental Addition and Subtraction

Mental addition and subtraction maths practice comprises arithmetical calculations using only the human brain, with no help from calculators, computers, or pen and paper. People use mental math when computing tools are not available, when it is faster than other means of calculation (for example, conventional methods as taught in educational institutions), or in a competition context.


Mental math often involves the use of specific techniques devised for specific types of problems.

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Mental Math Addition

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Below are the examples on mental math addition

Solved Examples

Question 1: Add 36 and 42.
Solution:
Step 1: Add the two ones' place digits: 6 + 2 = 8.

Step 2: Add the two tens' place digits: 3 + 4 = 7.

Step 3: The sum of the ones' place digits is less than 10.

Therefore answer is 78.

Question 2: Add 84 and 49.
Solution:
 
Step 1: Add the two ones' place digits: 4 + 9 = 13.

Step 2: Add the two tens' place digits: 8 + 4 = 12.

Step 3: The sum of the ones' place digits is a two-digit number so decrease the ones' place sum by 10: 13 - 10 = 3 and

increase the tens' place sum by 1: 12 + 1 = 13.

Step 4: Combine the tens' and ones' place sums.

Answer is 133.
 

Mental Math Subtraction

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Below are the examples on mental math subtraction

Solved Examples

Question 1: Subtract 26 from 75.
Solution:
 
Step 1: Subtract the two tens' place digits: 7 - 2 = 5

Step 2: Bottom one's digit is larger than the top one's digit.Decrease the answer for the tens' place by 1: 7 - 1 = 6 and

increase the top ones place value by 10: 5 + 10 = 15.

Step 3: Subtract the two ones' place values: 15 - 6 = 9

Step 4: Combine the tens' and ones' place value.

Answer is 49.
 

Question 2: Subtract 53 from 85.
Solution:
 
Step 1: Subtract the two tens' place digits: 8 - 5 = 3

Step 2: Subtract the two ones' place digits: 5 - 3 = 2

Step 3: Combine the tens' and ones' place value.

Answer is 32.
 


Mental Math Multiplication

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Below are the examples on mental math multiplication

Solved Examples

Question 1: Multiply 35 by 6
Solution:
Step 1: Multiply the one's digit by 6, 6 x 5 = 30

Step 2: Multiply the ten's digit by 6, 6 x 3 = 18

Step 3: Product of one's place is two digit 30, so add the ten's digit into 18, 18 + 3 = 21

Step 4: Combine the one's and two's place value

Answer is 210.



Question 2: Multiply 56 by 4
Solution:
Step 1: Multiply the one's digit by 4, 6 x 4 = 24

Step 2: Multiply the ten's digit by 4, 5 x 4 = 20

Step 3: Product of one's place is two digit 24, so add the ten's digit into 20, 20 + 2 = 22

Step 4: Combine the one's and two's place value

Answer is 224 


Mental Math Division

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Below are the examples on mental math Division

Solved Examples

Question 1: Divide 84 by 7
Solution:
Step 1: Divide the ten's digit by 7, $\frac{8}{7}$ = 1 with remainder 1

Step 2: Multiply 1 by 10, 1 x 10 = 10 and add it to one's place, 10 + 4 = 14

Step 3: Divide 14 by 7, $\frac{14}{7}$ = 2

Step 4: Combine the one's and two's place values

Answer is 12.


Question 2: Divide 96 by 6
Solution:
Step 1: Divide the ten's digit by 9, $\frac{9}{6}$ = 1 with remainder 3

Step 2: Multiply 3 by 10, 3 x 10 = 30 and add it to one's place, 30 + 6 = 36

Step 3: Divide 36 by 6, $\frac{36}{6}$ = 6

Step 4: Combine the one's and two's place values

Answer is 16


Mental Math Addition and Subtraction Practice Problems

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Practice Problems

Question 1: Add 25 and 23.
Question 2: Add 67 and 37.
Question 3: Subtract 14 from 62.
Question 4: Subtract 25 from 49.
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