Asked by aira


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?
Answered by Devron
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
Answered by aira
9,890 hours total*(60 min/1 hour)*(60 sec/1 min)= total time in seconds

is 35,604, 000 right?
Answered by Devron
Yes, 35,604,000 seconds, but what do you do with it once you have found the time that it takes in seconds?
Answered by aira
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?
Answered by Devron
You will get an answer that is very large, so you will have to use scientific notation. Report no more then 3 significant figures.
Answered by Devron
Yes, but only three significant figures. So, a number, decimal followed by two more numbers.
Answered by aira
so it will look like this :

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

-> 0.00106 is the final answer?

Answered by Devron
No, 1.06812e+16 is correct. But you are only suppose to report three significant figures: 1.07 e+16
Answered by aira
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?
Answered by Devron
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
Answered by Devron
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.
Answered by aira
I GOT IT. thank you so much !! best tutor out here
Answered by Devron
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.