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Bunuel

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

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The correct answer is E.
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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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1 hour = 3600 sec

20*3600=72000m/h

1/0.6=10/6 km in 1 mile

10/6*72000=120,000

E
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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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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

Correct answer - E
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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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