Cool math shortcuts

[BradyC]

The only one I remember you probably already know... Quick way to multiply 11 x any two-digit number... just add the two digits together and put the remainder in the middle. Ex: 11 x 23... 2 + 3 = 5 put the five in the middle 253... and if the middle number is two digits just carry it over to the left number like 11 x 58... 5 + 8 = 13 put the 3 in the middle and carry the one over the 5 which gives you 638. I know it's basic but I am noobish.