A river boat leaves Silver Town and travels upstream to Gold Town at an average speed of 6 kilometers per hour. It returns by the same route at an average speed of 5 kilometers per hour. What is the average speed for the round-trip in kilometers per hour?  Choose the correct choice from the following choices.
A) 5.5  B) 7.1  C) 7.2  D) 7.0  E) 8.0
Pick a number which is LCM of 5 and 6 = 30.   Upstream time = 30/6= 
<gadget id="calculator">30/6</gadget>
<output>5</output>
5 hrs   Downstream time= 30/5= 
<gadget id="calculator">30/5</gadget>
<output>6</output>
6 hrs   Total time= 11 hrs   Total distance = 60   5.5verage Speed = 60/11 = 5.5 km/hr
<result>A</result>
A river boat leaves Silver Town and travels upstream to Gold Town at an average speed of 6 kilometers per hour. It returns by the same route at an average speed of 5 kilometers per hour. What is the average speed for the round-trip in kilometers per hour?