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 3 kilometers per hour. What is the average speed for the round-trip in kilometers per hour?  Pick: A) 4.0 B) 3.8 C) 7.2 D) 7.5 E) 8.0
Pick a number which is LCM of 3 and 6 = 12.   Upstream time = 12/6= 
<gadget id="calculator">12/6</gadget>
<output>2</output>
2 hrs   Downstream time= 12/3= 
<gadget id="calculator">12/3</gadget>
<output>4</output>
4 hrs   Total time= 6 hrs   Total distance = 24   4.0verage Speed = 24/6= 
<gadget id="calculator">24/6</gadget>
<output>4</output>
4.0 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 3 kilometers per hour. What is the average speed for the round-trip in kilometers per hour?