When you ask someone “What time is it?”, you rarely hear “one thirty three”. But why? Perhaps they haven’t spent the time needed to keep their watch accurate to the minute. And perhaps they judge that “one thirty” is all the precision you really care about.

Yet when introduced to the volume of a ball, one hears it is 4/3 pi r3, rather than it is “one half the volume of the box the ball came in” (1/2 d3). As with “one thirty”, this simpler approximation is only off by 5%. But how often does one hear the simpler version? Often, it helps to get a simpler version of a lot of aspects we deal with , mainly to get the big picture, to recall at a later point of time and also to recount it effortlessly.

Most of the times we are so glued to the mathematical formulae and rote learning that goes along with a lot of stuff, that we miss the need to get estimation skills right and ultimately miss the learning .
To know more what I am talking about, one must read the book ' Innumeracy' by John Allen Paulos