## adajiamcneal one year ago Please explain to me how i got these wrong

2. anonymous

Whenever you perform these operations while using sig figs, your final answer should have the same number of sig figs as the number with the LEAST number of sig figs. So, let's take the third one for example.$485.369\div0.124=3914.26612903225806$Now, let's see how many sig figs we should be using. For 485.369, this number has 6 sig figs. For 0.124, this number has 3 sig figs. So, since 3 < 6, our final answer should have 3 sig figs. Rounding our answer, it will be 3.91E3 (notice how scientific notation makes this nice and neat for sig figs.

wait now im even more confused. . .

4. anonymous

Which part has you confused?

5. anonymous

First of all, do you see how 485.369 has 6 sig figs?

yeah i get that part. i dont understand what the e is for

7. anonymous

E is a shortcut for scientific notation. So, $$3.91E3 = 3.91\times10^3$$ (Sorry for being ambiguous, I should've made that more clear.)

oh ok lol . so let me try another one on my own but dont leave just incase i dont get it pleasee

9. anonymous

Sure :)

for A being that theres 2 significant figures on both sides does that mean the answer has 2?

11. anonymous

Wait, one more thing, I forgot to mention. The rule ^ works for multiplication and division. Addition and subtraction is slightly different. For addition and subtraction, you use the number of decimal places of the LEAST amount of accuracy. So, for example, if we had: $0.123 + 0.00132 = 0.12432$However, 0.123 has the least number of decimal places, so your answer will be rounded to 3 decimal places. So, we would get 0.124.

12. anonymous

So, for A, after you add them, your answer should have 1 number to the right of the decimal because 1.2 has the least precision.

oh ok so would that answer be 1.3 e3?

14. anonymous

The 1.3 would be fine. You wouldn't need the e3 because the number isn't bigger than that. The reason I used the e3 before is because my answer to that first example would've been 3910 (compared to the original of 3914.266). 391 are DEFINITELY significant figures, but the 0 is in a bit of a gray area. So, to make sure that it's clear that we mean for 3 sig figs, we use scientific notation and say 3.91 e3. The 3.91 part shows that you meant to have 3 sig figs, and the e3 (or $$10^3$$) makes clear what your actual number is because 3$$3.91 \times 10^3 = 3190$$, as we intended.

15. anonymous

Ignore the 3 before the $$3.91\times 10^3$$ at the end.

oh ok let me try one more?

17. anonymous

Sure!

b would be 0.1 right?

19. anonymous

Hmm, not quite. You're multiplying here, not adding, so your answer should have the same number of sig figs as the number with the $$least$$ sig figs.

20. anonymous

So, when adding and subtracting, you deal with decimal places. When multiplying and dividing, you deal with sig figs.

21. anonymous

Maybe this will help? http://chemed.chem.purdue.edu/genchem/topicreview/bp/ch1/sigfigs.html

22. anonymous

Ok, back.

it would be 0.16 ?

24. anonymous

Yes! Good job! Just to make sure you had the correct thought process, you got 0.156 in the original, both 1.2 and 0.13 had 2 sig figs, so your final answer will have 2 sig figs. 0.156 rounds to 0.16 when you have 2 sig figs.

Ok thank you so much :)

26. anonymous

np :)