Perform the calculation below as fast as you can, and using only mental arithmetic (so without pen and paper, or a calculator!).
Take 1000 and add 40.
Add 1000.
Add 30 and then add 1000.
Add 20.
Add 1000 and then add 10.
What is your answer :?:
Scroll down a bit to check it against the actual answer ;-)
Most people get 5000 as result, if they perform the calculation as fast as they can. But the answer is 4100. Because of the hurry, the tens and the hundreds are mixed up in the last step (4090 plus 10).
Clever eh :?: or Not as the case may be
So where you right or wrong :?:
TheGuru