Cindy paddles her kayak upstream at b 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?  Pick one
A) bnp	B) bn/p	C) (b + n)/p	D) bnp/(b + 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/b   similarly,   t2=d/n (as same distance has to be rowed)   also,   t1+t2=p   therefore,   p=(d/b)+(d/n)   =d(b+n)/bn   d=pbn/(b+n)=bnp/(b + n)
<result>D</result>
Cindy paddles her kayak upstream at b 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?