Multiplying by 11 - To multiply a two-digit number by 11, add the two digits together and place the result in the middle. For example, 32 x 11 = 352.
Squaring Numbers Ending in 5 - To square a number ending in 5, multiply the first digit by itself plus 1 and then add 25 to the end. For example, 35^2 = 1225.
Multiplying by 5 - To multiply a number by 5, simply divide the number in half and add a 0. For example, 5 x 24 = 120 (24 divided by 2 is 12, and adding a 0 gives you 120).
Multiplying by 9 - To multiply a number by 9, subtract the number from 10 and then subtract the result from the original number. For example, 9 x 7 = 63 (10 - 7 = 3, 7 - 3 = 4).
Adding and Subtracting Fractions - To add or subtract fractions with the same denominator, simply add or subtract the numerators and keep the denominator the same.
Multiplying by 4 - To multiply a number by 4, simply double the number twice. For example, 4 x 8 = 32 (8 doubled is 16, and 16 doubled is 32).
Multiplying by 25 - To multiply a number by 25, divide the number in half and then divide the result by 2. For example, 25 x 36 = 900 (36 divided by 2 is 18, and 18 divided by 2 is 9, so 900 is the answer).
Finding Percentages - To find a percentage of a number, multiply the number by the percentage and then divide the result by 100. For example, 20% of 80 = (20 x 80) / 100 = 16.
Dividing by 5 - To divide a number by 5, simply multiply the number by 2 and then move the decimal point one place to the left. For example, 65 divided by 5 = 13.