Cindy paddles her kayak upstream at a kilometers per hour, and then returns downstream the same distance at n kilometers per hour. How many kilometers upstream did she travel if she spent a total of p hours for the round trip?  Select.
A) mnp
B) an/p
C) (a + n)/p
D) anp/(a + n)
E) pm/n- pn/m
let t1 and t2 be the time taken to row upstream and downstream respectively   now,   t1=distance/speed=d/a   similarly,   t2=d/n (as same distance has to be rowed)   also,   t1+t2=p   therefore,   p=(d/a)+(d/n)   =d(a+n)/an   d=pan/(a+n)=anp/(a + n)
<result>D</result>
Cindy paddles her kayak upstream at a kilometers per hour, and then returns downstream the same distance at n kilometers per hour. How many kilometers upstream did she travel if she spent a total of p hours for the round trip?