it's more useful
if you use something easier to approximate it

which is what engineering is all about!
( Vipros. clever got me this far, then tricky got me in, Thu 28 May 2009, 9:53, 1 reply, 16 years ago)

One of the good things about science and engineering training
is the ability to estimate quantities with a decent degree of accuracy. You know intuitively your answer is in the right ballpark or not.

Unfortunately, one of my former students hadn't learned this skill, and had made the biggest error I've ever seen in an exam. His answer was wrong by 26 orders of magnitude! He'd made a mistake in the charge on the electron, and said it was 10⁷C instead of 1.6022 x 10^-19C, then used this in his subsequent calculations.

But he didn't notice that his answer was unfeasibly wrong.

To put the error into context, it's roughly the difference between the size of an atom and the size of the observable universe...
( K2k6 has a proper job these days, Thu 28 May 2009, 10:14, Reply)