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Re: The speed of light is approximately 1,86 [#permalink]
21 Mar 2013, 00:51

1

This post received KUDOS

This problem is fairly straightforward if you interpret the data given correctly.

We know that the speed of light is approximately \(1,86*10^5\) miles per second. If we rephrase it, we get that in 1 second we can travel \(1,86*10^5\) miles.

Since an hour is equal to 3600 seconds, based on our rephrasing, we're going to travel 3600 times the distance travelled in 1 second.

In short : \(3600*1,86*10^5 = 6,756*10^8\) which is close to answer choice E.

Re: The speed of light is approximately 1,86 [#permalink]
21 Mar 2013, 09:42

Expert's post

surya167 wrote:

Fantastic, thanks Brunel.

The other collection of similar conversion problems are of great help!

Conversion questions can give some people fits, but remember that it will often ask you to convert from something per second to something per hour, which will always be x3600 (even during daylight savings time and even during leap years). That's the only one you need to know, which is basically multiplying by ~3.5 and then add 1,000.

1.86 is about 2, multiplying by ~3.5 gives you something a little under 7. There will only be one answer in the vicinity, so you can approximate this without ever putting pen to paper. If there are two answers that are close, then feel free to do the exact equation.

Anything that is not time will have units (example 5,280 feet in a mile, 1,000 meters in a kilometer, etc).

Personally, I'd love to see a question that crosses metric with imperial, such as "Usain Bolt runs at 10.16 meters/second, what is his speed in feet/second" but the GMAT doesn't cross these two systems (although it uses both in separate questions)

Re: The speed of light is approximately 1,86 [#permalink]
25 Aug 2014, 10:11

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Re: The speed of light is approximately 1,86 [#permalink]
15 Apr 2015, 09:59

carcass wrote:

The speed of light is approximately 1,86 * 10^5 miles per second. This approximate speed is how many miles per hour?

(A) 1,11 * 10^7

(B) 6,70 * 10^7

(C) 1,11 * 10^8

(D) 1,86 * 10^8

(E) 6,70 * 10^8

The easiest way to answer this question is by POE, it does not require any calculation (answered in 30seconds). In one hour there are 3600 seconds, therefore speed in miles/hour will be.

(1.86*10^5)*3600 = (1.86*10^5)*(3.6*10^3) = some number*10^8...

The key is realizing that the "some number" has to be bigger thatn 1.86 (because 1.86*3.6), and the only answer that fits that is E.

Hope it helps

gmatclubot

Re: The speed of light is approximately 1,86
[#permalink]
15 Apr 2015, 09:59

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