How to round 009999991 to 4 significant figures

Answer 1

I just did this problem for chemistry class!

.009999991 to 4 sig figs is like this:

.00 (these zeros are leading zeros, they don't count) so .009999991 is 7 sig figs.

.009999 is 4 sig figs. One problem... you must round using the figure that came after the cut off point which was a 9 so you want to round the next 9 to 10 but then you have a 9 again in front of that. OH NO! don't stress :)

.009999 becomes .009990 but you need to make a ten so then the next 9 becomes a 10 and so on until you run out of 9's leaving you with .009999=.0010000 Still not done though! Trailing zeros after a number after a decimal are significant! So just take off one of the zeros leaving you with .01000

4 sig figs! tadah :D