Here are some ways to calculate easily in math:

1. Addition - Round up to the nearest number or multiple of 10, add them, and then adjust the deficiency. For ex. 48 rounds up 50, 28 rounds up 30, 67 rounds up to 70

2. Subtraction - Round the number being subtracted to zero. Then subtract the rounded number from the larger number. For example, 44 rounds up to 40, 23 rounds up to 20, 14 rounds to 10

3. Multiplication: - Divide numbers into tens and ones place, multiply then add results. Ex. 5X8= split 5 into 50 and 8, then, add the results

4. Division: - Divide numbers into their ten and ones place again, divide them, then multiply results. Ex. 7/2 = spliting 7 into 70 and 2 

5. Square Roots: - Estimate square root of number by finding the nearest perfect square and then subtracting it from nearest perfect number. 

6. Multiply by 11 without writing it down:
To multiply any digit by 11, add the digits together and place the result in between
Ex. 54x11 = 594   5+4 = 9       594

7. Use 9 to your advantage:
If you're multiplying by 9, it is easier than you think. For single digits, just subtract 1 and then subtract 9. Ex. 9x4 = 4-1 = 3   9 - 3 = 6     36

8. Square numbers that end in 5: - Square any number that ends in 5
Ex. 45(squared) = 4x5 + 5x5 = 2025


9.  Estimate percentages in your head: - Calculating percentages is mental and easier than you think
Ex. 10% of 340 is = 34 because 340/10
20% of 60 = 10% of 60 x2 = 120/10 = 12

10. Double numbers by breaking them apart:​ - Doubling numbers rapidly could be benefical for budgeting, scheduling, or estimating. Ex. 183 x 2 = 180 x 2 = 360 + 3x2 = 366