Have you always wanted to solve complex mathematical calculations in a blink of an eye? But end up solving the questions wrong? Don’t worry! We are here to simplify your job and make you a math genius. In this blog, we will learn about some easy yet effective mental math shortcuts that help solve complex mathematical calculations in seconds.
20 Mental Math Shortcuts to Solve Complex Calculations
| Category | Shortcut | Example |
|---|---|---|
| Addition Shortcuts | Adding 9 – Add 10, then subtract 1 | 47 + 9 → (47 + 10) - 1 = 56 |
| Adding 11 – Add 10, then add 1 | 34 + 11 → (34 + 10) + 1 = 45 | |
| Subtraction Shortcuts | Subtracting 9 – Subtract 10, then add 1 | 56 - 9 → (56 - 10) + 1 = 47 |
| Subtracting 11 – Subtract 10, then subtract 1 | 45 - 11 → (45 - 10) - 1 = 34 | |
| Multiplication Shortcuts | Multiply by 5 – Divide by 2, then multiply by 10 | 24 × 5 → (24 ÷ 2) × 10 = 120 |
| Multiply by 9 – Multiply by 10, then subtract the number | 7 × 9 → (7 × 10) - 7 = 63 | |
| Multiply by 25 – Divide by 4, then multiply by 100 | 16 × 25 → (16 ÷ 4) × 100 = 400 | |
| Multiply by 12 – Multiply by 10, then add twice the number | 15 × 12 → 150 + 30 = 180 | |
| Multiply by 15 – Multiply by 10, then add half the number | 20 × 15 → 200 + 100 = 300 | |
| Division Shortcuts | Divide by 5 – Multiply by 2, then divide by 10 | 75 ÷ 5 → (75 × 2) ÷ 10 = 15 |
| Divide by 10 – Move decimal one place left | 450 ÷ 10 → 45.0 | |
| Divide by 4 – Halve the number twice | 32 ÷ 4 → (32 ÷ 2) ÷ 2 = 8 | |
| Percentage Shortcuts | Finding 10% – Move decimal one place left | 250 → 25 |
| Finding 20% – Find 10%, then double it | 250 → (10% = 25) × 2 = 50 | |
| Finding 50% – Divide by 2 | 80 → 80 ÷ 2 = 40 | |
| Finding 25% – Divide by 4 | 100 → 100 ÷ 4 = 25 | |
| Squares & Square Roots | Square of numbers ending in 5 – Multiply first digit by its successor, then append 25 | 35² → (3 × 4) = 12 → 1225 |
| Rounding & Estimation | Estimating sums – Round numbers to nearest ten before adding | 48 + 27 ≈ 50 + 30 = 80 |
| Estimating products – Round numbers to nearest ten before multiplying | 48 × 27 ≈ 50 × 30 = 1500 | |
| Money Math Shortcuts | Calculating discounts – Find 10% and double it | 20% off Rs50 → 10% = Rs5 → Rs10 off |
You can make your life easier by learning addition shortcuts, subtraction shortcuts, multiplication shortcuts, division shortcuts, percentage shortcuts, squares & square roots shortcuts, and many others below.
Addition Math Shortcuts
Adding 9
Do you know the easiest way to add 9 to any number? It’s simpler than you could have ever imagined. Let’s assume you want to add 9 to 47. Then you simply add 10 to 47 and subtract 1 from the resultant number. The steps will look like this: (47 + 10) – 1 = 56. The answer is 56.
Adding 11
If you ever find adding 11 to any number time-consuming, we are going to tell you a simple trick that will save you precious time. Let’s assume you want to add 11 to 34. Simply add ten to the number and then add 1 to the resultant number. The steps will look like this: (34 + 10) + 1 = 45. The answer is 45.
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Subtraction Math Shortcuts
Subtracting 9
Are you aware of an easy method to subtract 9 from any number? Again, it’s a child’s play. Let’s assume you want to subtract 9 from 56. In that case, just add ten to the number and then add 1 to the resultant number. The steps will look like this: (56 – 10) + 1 = 47. The answer is 47.
Subtracting 11
Do you find subtracting 11 from any number tedious? Here’s an easy method for you. Let’s assume you want to subtract 11 from 45. Then just need to subtract ten from the number and then again subtract 1 from the resultant number. The steps appear like this: (45 – 10) – 1 = 34. The answer is 34.
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Multiplication Math Shortcuts
Multiplying by 5
Are you aware of the easiest way to multiply any number by 5? We have one for you. Let’s say you want to multiply 24 by 5 then simply divide 24 by 2 and multiply the resultant by ten. The steps appear like this: (24 ÷ 2) × 10 = 120. The answer is 120.
Multiplying by 9
Do you know the easiest method to multiply any number by 9? We have one for you. Let’s assume you want to multiply 7 by 9. In that case, you need to multiply 7 by 10 and subtract the same number (here 7) from the resultant number. The steps will look like this: (7 × 10) – 7 = 63. The answer is 63.
Multiplying by 25
Are you aware of the brilliant method to multiply any number by 25 within a fraction of a second? This method is going to make your life easier due to its universal application. Let’s say you want to multiply 16 by 25. Then you have to divide 16 by 4 and multiply the resultant number by 100. The steps will appear like this: (16 ÷ 4) × 100 = 400. The answer is 400.
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Division Math Shortcuts
Dividing by 5
Do you know the easiest method to divide any number by 5? We have one for you. This method is going to make calculation a lot easier. So, let’s assume you want to divide 75 by 5. In that case, you have to multiply 75 by 2 and then divide the resultant number by 10. The steps will appear like this: (75 × 2) ÷ 10 = 15. The answer is 15.
Dividing by 10
Do you know the right method to divide any number by 10? This method is going to make your life easier due to its universal application. Let’s assume you want to divide 450 by 10. In that case, you have to simply move the decimal point one place to the left of 450. The calculation will look like this: 450 ÷ 10 = 45.0. So, the answer is 45.
Dividing by 4: Halve the number twice. (e.g., 32 ÷ 4 = 16 ÷ 2 = 8)
Do you know the best way to divide any number by 4? Let’s assume you want to divide 32 by 4. In that case, you just need to halve 32 twice. The calculation will look like this: 32 ÷ 4 = 16 ÷ 2 = 8. The answer is 8.
Percentages Math Shortcuts
Finding 10%: To find 10%, move the decimal point one place to the left. (e.g., 250 → 25)
Do you know finding 10% of any number is one of the easiest calculations to do in life? Simply move the decimal point one place to the left of the number. Let’s assume you want to find the 10% of 250. The answer is 25.0 i.e., 25.
Finding 20%: Find 10% and double it. (e.g., 250 → 25 × 2 = 50)
Finding 20% will require you to add one more step after finding 10% of the number. Simply find the 10% of the number by moving the decimal point one place to the left of the number. After this, multiply the resultant number by 2. Let’s say you want to find the 20% of 250. In that case, 10% of 250 will be 25. Now multiply by 25 by 2. The 20% of 250 comes is 50.
Finding 50%: Divide the number by 2. (e.g., 80 → 80 ÷ 2 = 40)
Calculating 50% of any number is one of the simplest things to do. Simply divide the number by 2. Let’s assume you want to find the 50% of 80. So, you have to divide 80 by 2. The answer is 40.
Finding 25%: Divide by 4. (e.g., 100 → 100 ÷ 4 = 25)
To find 25% of any number you have to divide the number by 4. Let’s say you want to find 25% of 100 then you have to divide 100 by 4. The answer is 25.
Squares and Square Roots Math Shortcuts
Square of a number ending with 5: Multiply the first digit by itself plus one, then append 25. (e.g., 352=3×4=12352=3×4=12→ 1225)
Ever thought how easy it could be to find the square of a two-digit number ending with 5? Let’s assume you want to find the square of 35. Simply multiply the first digit from left by its successor. Then append 25 to the resultant number. Here, the first digit from left is 3. So, multiplying 3 by its successor 4 becomes 12. After appending 25 to 12, we get 1225. So, the answer is 1225.
Miscellaneous Math Shortcuts
Multiplying by 12: Multiply by 10 and add twice the original number. (e.g., 15 × 12 = 150 + 30 = 180)
Want to easily multiply any number by 12? Simply multiply the number by 10 and add twice the original number. Let’s assume you want to multiply 15 by 12. So, multiplying 15 by 10 equals 150. Now add twice the 15 = 150 + 30. This comes to 180.
Multiplying by 15: Multiply by 10 and add half of the original number. (e.g., 20 × 15 = 200 + 10 = 300)
Want to easily multiply any number by 15? Simply multiply the number by 10 and then add half of the resultant number. Let’s assume you want to multiply 20 by 15. So, multiply 20 by 10 equals 200. Half of 200 equals 100. So, adding 200 to 100 becomes 300.
Rounding and Estimation Math Shortcuts
Estimating sums: Round each number to the nearest ten before adding. (e.g., 48 + 27 ≈ 50 + 30 = 80)
Want to find the estimated sum of numbers? Try rounding each number to the nearest ten before adding. Let’s say you want to find the round off of 48+27. Then find the round off to the nearest ten of both the numbers. This gives us 50+30. So, the estimate sum of 48+27 ≈ 50 + 30 = 80)
Estimating products: Round each number to the nearest ten before multiplying. (e.g., 48 × 27 ≈ 50 × 30 = 1500)
Want to find the estimated product of numbers? Try rounding each number to the nearest ten before multiplying. Let’s say you want to find the round off of 48 × 27. Then find the round off to the nearest ten of both the numbers. This gives us 50 × 30. So, the estimated product of 48×27 ≈ 50 × 30 = 1500.
Money Math Shortcuts
Calculating discounts: To find 20% off, find 10% and double it. (e.g., for Rs.50, 10% is Rs.5, so 20% is Rs.10 off.)
Have you ever struggled with calculating discounts on your favourite apparel or goods? This calculation shortcut will make your task a cakewalk. If you are looking to find 20% discount on any product, simply find 10% of the product value and double it. Let’s say you want to find the 20% of a product worth Rs 50. So, its 10% will be 5 when we move the decimal point one place to the left of the number. Now double the number and you get 10 as your answer.
