A rower can row 5 km/h in still water. When the river is running at 2 km/h, it takes the rower 1 hour to row to Big Rock and back. How many kilometers is it to Big Rock? Choices:
A) 1.5	B) 1.8	C) 2.1	D) 2.4	E) 2.7
Let x be the distance to Big Rock.   time = x/3 + x/7 = 1   x = 21/10= 
<gadget id="calculator">21/10</gadget>
<output>21/10 = around 2.1</output>
2.1 km   The answer is 2.1.
<result>C</result>
A rower can row 5 km/h in still water. When the river is running at 2 km/h, it takes the rower 1 hour to row to Big Rock and back. How many kilometers is it to Big Rock?