Find the answer using the correct number of significant figures:
33.65-15.5801+8.7
*Step By Step Answer Please :)

Question

Find the answer using the correct number of significant figures:
33.65-15.5801+8.7
*Step By Step Answer Please :)

lgbasallote · Answer

first...do you know which one has the LEAST number of significant figures?

anonymous · Answer

8.7

lgbasallote · Answer

right...how many significant figures does that have?

anonymous · Answer

2

lgbasallote · Answer

now...which one has the smallest number of decimal places?

anonymous · Answer

8.7???

lgbasallote · Answer

yep! how many decimal places does it have?

anonymous · Answer

1

lgbasallote · Answer

right...so since you're adding and subtracting significant figures...all numbers must have the same decimal place as the least..in this case 1...are you following?

anonymous · Answer

All the numbers in the equation?? Like 33.65 and 15.5801

lgbasallote · Answer

so 33.65 becomes 33.7

15.5801 becomes 15.6

8.7 remains as 8.7

now do the operation

33.7 - 15.6 + 8.7

does that help?

anonymous · Answer

Yes

anonymous · Answer

So it would be 26.8?

lgbasallote · Answer

wait...let me see

shane_b · Answer

You round only at the end though...you add/subtract normally until then.

lgbasallote · Answer

my google calculator agrees

lgbasallote · Answer

well it's a matter of sigfigs...so you *have* to round off...

shane_b · Answer

At the end :)  Otherwise, you're inducing more error along the way.  That's how I was taught anyway

lgbasallote · Answer

nope...when adding and subtracting sigfigs you have to keep the decimal places same

lgbasallote · Answer

http://www.usca.edu/chemistry/genchem/sigfig2.htm

shane_b · Answer

From wiki: "When performing a calculation, do not follow these guidelines for intermediate results; keep as many digits as is practical to avoid rounding errors"

That's how I was taught also...and it makes sense to keep the intermediate error as low as possible.

lgbasallote · Answer

well fine do it your way :p

shane_b · Answer

hehe...that's my story and I'm sticking to it!

lgbasallote · Answer

hehe anyway..i stand corrected

shane_b · Answer

It just happened to work out right both ways this time ;)

shane_b · Answer

err I meant "the same"

lgbasallote · Answer

it usually does

shane_b · Answer

I'd agree with that...as long as we're only talking about adding/subtracting a few values

lgbasallote · Answer

yup

anonymous · Answer

Thanks for the help :)