Hi, I am taking a practice test and I have no idea why it came to be this answer can someone explain it to me.

How many significant figures should be reported for the difference between 235.7631 and 235.57?

The answer was 2. Why is that, I would expect it to have at least 5 sig figs.

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Three different samples were weighed using a different type of balance for each sample.
The three were found to weigh 0.1568934 kg, 1.215 mg, and 2458.1 g. The total mass of
the samples should be reported as
a. 2614.994615 g. b. 2614.9946 g. c. 2614.995
d. 2615.0 g. e. 2615 g.

With this problem Do I just add all of the samples? If so, I added them up and it gives me a total of 2459.471. The answer is D

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The age of a wooden artifact was determined by carbon-14 dating. Three different
measurements gave values of 6295, 4815, and 5485 years. Its age would best be
reported as
a. 5531.7 years. b. 5532 years. c. 5530 years.
d. 5500 years. e. 5000 years.

On this one, do I just add all the values and take the average? And the answer for this one is E

can someone explain how they got the answers?

Problem 1: I agree with you. I would have thought 5 sig figs as well.


Problem 2: The answer is D.

You can't just add them all up since they are all different units.

The Answer is D: 2615.0 g

0.1568934 kg = 156.8934 grams
1.21500 mg = 0.001215 grams
2458.1 g = 2458.1 grams

Total = 2614.995 grams

The answer is D though, not C because you have to account for significant digits (figures)

Problem 1: I agree with you. I would have thought 5 sig figs as well.


I know, I just don't know where they came up with just 2 sig figs


Problem 2: The answer is D.

You can't just add them all up since they are all different units.

The Answer is D: 2615.0 g

0.1568934 kg = 156.8934 grams
1.21500 mg = 0.001215 grams
2458.1 g = 2458.1 grams

Total = 2614.995 grams

The answer is D though, not C b/c you have to account for significant digits (figures)

Ah... I see thank you... ** "duh" to myself **:D

I find out why the first question has 2 sig figs

235.7621
-235.57
________
000.39.?

And there are 2 :)