Scientific notation and rounding question

Posted on 2014-04-03 10:04:00 in Chemistry by STEPHANIE

I'm doing my chemistry homework and I ran into a problem I don't understand. The answers that I'm getting at in scientific notation, but I wasn't sure how I should round it. The answer I got for the problem is 7.015538291x10^24. Every website I looked at said it should be 7.02x10^24. But that doesn't make sense to me because you get ^24 because there is 24 0s after the last significant figure. But if you round it, shouldn't you add to the 24 to make up for the numbers you rounded? For example my rounded answer should be 7.02x10^31 because there was already 24 and then I added 7 to it because i rounded to the hundreds place, and there are 7 numbers before the hundreds place in the full answer. If i made it ^31 the the answer would be like this compared to the full answer:

7.020000000000000000000000000000000

7.015538291000000000000000000000000

But if I do what everything else suggests then it would be like this:

7.0200000000000000000000000

7.05538291000000000000000000000000

Am I right that i should change the exponent, or should I leave it the same? If i should leave it the same please explain why. THANK YOU :)

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