10.0 kg octane are burned resulting in 35,000 J being released (made-up problem)?

Question

Convert to calories (C)
I did the converting (J ---> cal. = 4.184 J / 1 cal.) and I got 8126 cal.

How do I round the problem correctly?

Answer 1

I think the conversion factor you used is somewhat incorrect...

1 cal = 4.186 J, not 4.184 J...

In the end, the answer should be 8361 cal or 8.361 kcal.

The solution:

35000 J * (1 cal / 4.186 J) = 8361 cal.

Answer 2

It is 4.184, not 4.186 as the previous answer claims.

In any case, you have 3 significant digits in 10.0 kg., so you must round your answer to 3 sig. digits as well.

So 8130 cal is the correct answewr