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Old 07-25-2007   #1
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Default Math Help Please ?

A light-year is the distance that light travels in one year. Find the number of miles in a light-year if the light travels 1.86 x 10^5 miles per second. a. 5.9 x 10^12b. 5.9 x 10^7c. 5.9 x 10^5
Old 07-25-2007   #2
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Old 07-25-2007   #3
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in one day 60*60*24=86400 secsin a 365 day year 31536000 secs or 3.15*10^7so in a year light goes 1.86 * 3.15 * 10^12answer a
Old 07-25-2007   #4
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Old 07-25-2007   #5
Benjamin G
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Basically you're taking the seconds in a year multiplied by 1.86 x 10^5. Without doing the actual math, you want to look at the powers. The answer should be some result to the power of each of your factors added together. For instance: 10x100= 1000. Or 1x10^1 * 1x10^2 = 1x10^3. So c is out because it shows no increase. b is out because seconds would have to be less than 10^2 or 100 and we know there are more than 100 seconds in a year. So a has to be the answer. Considering that 10^12 - 10^5 is 7. It is reasonable to think that the number of seconds in a year is in the 10^7 range, this answer makes sense.

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