The number of significant figures in 0.40 is:
There are 2 sig. digs. The way I usually explain this one is to ask the question "Why would we bother to write the 0 after the 4 if it wasn't significant? After all 0.40 = 0.4!"Originally Posted by pocahontas
The reason the 0 before the decimal point is not significant is a little trickier to explain. Basically, it's just a place-holder. An example of why we don't count this digit as significant appears in a similar problem: how many sig. digs. does 4.0 have? We obviously wouldn't say 3 here because to write 04.0 is ludicrous (though the first 0 is, in fact, known with certainty). The reasoning for 0.40 is similar, though obviously much less trivial.
Hey. Sig Figs can be confusing but heres a few rules that make it simple.
When you get a number without a decimal point, look to the right and begin counting from the first non-zero digit
ex: 40001 has 5 sig figs whereas 400010 has 5 sig figs as well
*Note: You never see a number written like 010, but because you count from right to left, it would have 2 sig figs. (I just thought that might clarify the rule a little bit)
When you get a number with a decimal point, count from the first non-zero digit on the left
ex: .010 has 2 sig figs, and 1.010 has 4 sig figs .001 has 1 sig fig
--> ---> ->
I believe if you remember the right to left / left to right rule...you should be fine