how to square large numbers

I know up to 152, above that I need a calculator. Until today. via lifehacker, john graham-cumming gave us a great method using mental arithmetic. So if I want to find out what is 482.

  • round up the number to be squared to the next 10 = 50
  • how many to do the round up? 50-48=2
  • take 2 from 48 = 46
  • multiply 46×50=2300 (it’s easy to do in the head)
  • add 22 2300+4=2304

Seems more trouble than it’s worth.