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A man cycles from home to work at 15 km/h and returns at 20 km/h. If the next day he...

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user158 | eNoter

Posted July 4, 2013 at 5:19 AM via web

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A man cycles from home to work at 15 km/h and returns at 20 km/h. If the next day he increases the speed of going by 5% and decreases the speed of coming by 10%, what is his average speed.

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted July 4, 2013 at 5:23 AM (Answer #1)

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The man cycles from home to work at 15 km/h and returns at 20 km/h.

If the speed of going is increased by 5% an the speed at which he returns is decreased by 10%, the respective speeds are 15*(1+0.05) = 15.75 km/ h and 20*(1 - 0.1) = 18 km/h.

The average speed is now (15.75 + 18)/2 = 16.875 km/h

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deviabirami | eNotes Newbie

Posted July 4, 2013 at 4:26 PM (Answer #2)

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Going to work km/h    Coming to home km/h              Average km/h

15                                    20                                15*20/2= 17.5 

Next day increases 5%    decreases by 10%

15+(15*5/100)               20-(20*10/100)

15+.75                           20-2 

15.75                             18                             15.75*18/2= 16.875

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