Casting out 9's to easily Double check the answer

Throwing out Nines (9’s) After applying an arithmetic operation to two operands and getting a result, you can use this procedure to i... Read more »

Finding the number of factors of any number

If a number can be expressed as a product of two whole numbers, then the whole numbers are called factors of that number. In other wo... Read more »

Converting Repeating Decimals into Fractions

It is fairly easy to take a fraction and turn it into a repeating decimal by hand. This is simple division. But being able to go in the ... Read more »

Rule of 72: Estimation of Compound Interest and Time

Effect of Compounding The Rule of 72 is a good quick math shortcut to estimate the effect of any growth rate, from quick financial calc... Read more »

Easy trick to mentally calculate percentages

Situation when we need to calculate the percentages in our mind are quite common. While calculating the VAT, Insurance premium or Tips at ... Read more »