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# The Earth travels around the Sun at an approximate speed of 20 miles p

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Math Expert
Joined: 02 Sep 2009
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The Earth travels around the Sun at an approximate speed of 20 miles p [#permalink]

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02 Dec 2014, 08:14
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Difficulty:

45% (medium)

Question Stats:

59% (01:02) correct 41% (01:11) wrong based on 210 sessions

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Tough and Tricky questions: Arithmetic.

The Earth travels around the Sun at an approximate speed of 20 miles per second. This speed is how many kilometers per hour? [1km = 0.6 miles]

A) 2,000
B) 12,000
C) 43,200
D) 72,000
E) 120,000

Kudos for a correct solution.

Source: Chili Hot GMAT
[Reveal] Spoiler: OA

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Re: The Earth travels around the Sun at an approximate speed of 20 miles p [#permalink]

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02 Dec 2014, 09:09
This is a dimensional analysis or unit-converting problem. Let's start:

20miles/second to miles/hour: 20mi/s*3600s/hr
miles/hour to kms/hour: 20mi/s*3600s/hr*1km/0.6mi

Doing this cancels out the units of miles (mi) and seconds (s) and yields km/hr and we end up with 120,000km/hr
Choice E

Note that its easier to do 3600s/hr*1km/0.6mi than to multiply anything else--so do this step first.
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Re: The Earth travels around the Sun at an approximate speed of 20 miles p [#permalink]

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02 Dec 2014, 19:15
2
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1 Km = 0.6 Miles

20 Miles = $$\frac{20}{0.6}$$ Kms

Km/Hr speed $$= \frac{20}{0.6} * 60 * 60 = 200 * 10 * 60 = 120000$$
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Math Expert
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Re: The Earth travels around the Sun at an approximate speed of 20 miles p [#permalink]

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03 Dec 2014, 06:58
Bunuel wrote:

Tough and Tricky questions: Arithmetic.

The Earth travels around the Sun at an approximate speed of 20 miles per second. This speed is how many kilometers per hour? [1km = 0.6 miles]

A) 2,000
B) 12,000
C) 43,200
D) 72,000
E) 120,000

Kudos for a correct solution.

Source: Chili Hot GMAT

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Re: The Earth travels around the Sun at an approximate speed of 20 miles p [#permalink]

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09 Dec 2014, 04:59
1km=(6/10) mile hence 1 mile=(1km/(6/10))=(10/6)mile. Now Sun speed for an hour is equal to 3600 (number of seconds in an hour)*20 = 72 000 mile. To convert to km simply multiply this by (10/6). Hence (72 000 * 10)/6 = 12 000*10=120000. Hope it is clear
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Re: The Earth travels around the Sun at an approximate speed of 20 miles p [#permalink]

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09 Dec 2014, 20:42
1 hour = 3600 sec

20*3600=72000m/h

1/0.6=10/6 km in 1 mile

10/6*72000=120,000

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Re: The Earth travels around the Sun at an approximate speed of 20 miles p [#permalink]

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29 Nov 2015, 10:45
20miles/sec * 60sec/min * 60min/h = 72,000 miles / hour

now, 72,000 miles/hour * 10km/6miles
simplify miles with miles, 6 with 72, and get 12,000 * 10km/hour => 120,000.00 km
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Re: The Earth travels around the Sun at an approximate speed of 20 miles p [#permalink]

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02 Apr 2016, 11:37
To calculate the equivalent of kilometres in a mile
20 miles = 20*(0.6)^-1 = 33.3334 kilometres
In 1 hour there are 60 minutes
In 1 minute there are 60 seconds
So in 1 hour there are 3600 seconds
Speed in kmph = 33.3334 * 3600 = 120000

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Re: The Earth travels around the Sun at an approximate speed of 20 miles p [#permalink]

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01 Sep 2017, 23:16
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Re: The Earth travels around the Sun at an approximate speed of 20 miles p [#permalink]

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02 Sep 2017, 04:07
This question can be solved by unitary method
0.6 miles =1 km
So 20 miles =?
Number of kilometers = 20/0.6=200/6

Now to convert Seconds into hours we have to divide the second by 3600
So the speed will be =200/6*3600=12000
Hence E
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Re: The Earth travels around the Sun at an approximate speed of 20 miles p   [#permalink] 02 Sep 2017, 04:07
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