# chemistry

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Light travels at 3.00 x 10^8 m/s. If the starlight from the Unicorn galaxy takes 1 year 47 days and 2 hours to reach us. How far away is it in kilometers?

• chemistry -

1 year=365 days

365 + 47=412 days total

412 days*(24hours/1 day)= 9,888 hours

9,888 hours + 2 hours=9,890 hours total

9,890 hours total*(60 min/1 hour)*(60 sec/1 min)= total time in seconds

3.00 x 10^8 m/s*total time in seconds= distance in meters

distance in meters*(1 kilometer/1,000m)= distance in kilometers

• chemistry -

9,890 hours total*(60 min/1 hour)*(60 sec/1 min)= total time in seconds

is 35,604, 000 right?

• chemistry-aira -

Yes, 35,604,000 seconds, but what do you do with it once you have found the time that it takes in seconds?

• chemistry -

I multiply 35,604,000 by 3.00 x 10^8 to find out the distance in meters?

which gives me 1.06812e+16??

is that right?

• chemistry -

You will get an answer that is very large, so you will have to use scientific notation. Report no more then 3 significant figures.

• chemistry -

Yes, but only three significant figures. So, a number, decimal followed by two more numbers.

• chemistry -

so it will look like this :

distance in meters (1.06)*(1 kilometer/1,000m) = distance in kilometers

-> 0.00106 is the final answer?

• chemistry -

No, 1.06812e+16 is correct. But you are only suppose to report three significant figures: 1.07 e+16

• chemistry -

yeah, but I'm very confused on how to get the final answer. Do i take 1.07e+16 and multiply it by a thousand to get km?

• chemistry -

No. 1.07 x 10^16 is in meters; you have to take the whole thing and divide it by 1,000, not just 1.07.

So, 1.07 x 10^16 m*(1km/1,000m)= your answer in Km

****Notice how the m's cancel and you are only left with km.

The FINAL ANSWER SHOUD BE 1.07 x 10^13

• chemistry -

1,000meters=1km

So, you have to make this relationship a fraction.

1,000m/1km.

But how do I organize it in a way that meters goes away and kilometers remain?

(1km/1000m)

So if I multiply the ration this way, by my intermediate answer that is in meters, then the meters cross cancel and you are only left with meters.

I hope this makes more since.

• chemistry -

I GOT IT. thank you so much !! best tutor out here

• chemistry -

You are too nice. At least you can understand my typos. When I help others on another forum, I can edit my answers, so I do not look like an idiot, but on this forum I can not.

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