Blows my mind

It truly amazes me how people learn and calculate in different manners. J has always computed his math problems in a different way than myself; but it struck me the other night that I honestly CAN'T compute in the same way. J uses the "rounding method" He's always used 5's or 10's to round and than add or subtract to get answers for large digit addition and subtraction problems and he can spit them out faster than I can use the calculator. He's now on 3 digit division and he uses the same method of rounding. The funny thing is when I showed him how I calculate the problems, he was amazed that you could do it my way and he even had me use the calculator to ensure I had done it correctly.