This exercise must be done in your head only . Do NOT use paper and pencil or a calculator. Try it!
Take 1000 and add 40 to it. Now add another 1000 . Now add 30 . Add another 1000 . Now add 20 . Now add another 1000 Now add 10.
What is the total?
Did you get 5000 ?
Correct answer is 4100!!!