Just a little highschool algebra (simple enough to do in your head even) reveals the trivial trick to this one. By throwing in a couple of extra steps and later removing their effect, it looks almost mystical on your calculator.
Member Rara Avis
Mumbai, India : now in Belgium
It would work for any arbitrary number of digits, Sudhir. You just have to change the multiplication base (Note that 80 * 250 / 2 = 10,000, which is what moves the first three digits to the left so that adding the last four digits will appear.)
Between the Lines