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Homework Help: Test - Doubt

  1. Jun 3, 2013 #1
    1. 2 questions, one asked for the temperature of the water max density and the other one a Potency question which the awnser was 1125...

    Trying to be funny( hahaha funny as **** ) i wrote 1124,999... as the anwser, since 1124,999...=1125 but my prof. said it was wrong this statement in physics because of some rules, i want to understand why if someone could tell me, the other doubt is that i wrote that the water max density was 3,98ºC he said it is 4ºC then he took 0,5 out of the question that worthed 2...

    Can someone agree with me that in both situations i was right? ahahhha
  2. jcsd
  3. Jun 3, 2013 #2
    Please don't bold your entire post. It's completely unnecessary and makes it hard to read.

    Your problem in both cases was probably significant figures. While 1125 = 1124.99... exactly in mathematics, they have different numbers of significant figures. 1125 has four significant figures, 1124.99... has infinite significant figures. Clearly no experiment has infinite precision. Likewise for the second problem: 3.98 has three significant figures and 4 has one. I would assume that the quantities in your question had one significant figure and so your answer should have had one significant figure. Of course, since you have not given any of the reasons your professor gave you, this is only an educated guess.

    You would be much better advised to speak to your professor if you have questions about his marking than having other people try to guess with limited information.
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