🧮 Mental math
Tricks that make numbers in your head quick enough to be fun.
- 🧮 Mental mathMultiply any two-digit number by 11Split the digits apart and put their sum in the middle.
- 🧮 Mental mathSwap a percentage to make it easy8% of 25 is hard. 25% of 8 is easy, and it's the same number.
- 🧮 Mental mathSquare numbers ending in 565² in two seconds: multiply the front by the next number up, then write 25.
- 🧮 Mental mathWork out a tip in your headMove the decimal point once, then double it or add half.