Answers

2015-11-17T21:01:30+05:30
Speed₁ = 9 km/h = 150 m/min 
time₁ = 10 min 
speed₂ = x m/min
time₂ = 20 min 
average speed = 12 km/h = 200 m/min
therefore ,
average = total speed / total time 
200 = 150 + x / 20 + 10
200 = 150 +x / 30 
200 * 30 = 150 + x
6000 = 150 +x 
6000 - 150 = x
5850 = x 
therefore the speed is 5850 m/min = 351 km/h
the answer is 351 km/h
   i hope it helps.......................^_^ 


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