Cindy paddles her kayak upstream at m 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?
$$A.\ mnp$$
$$B.\ \frac{mn}{p}$$
$$C.\ \frac{m+n}{p}$$
$$D.\ \frac{mnp}{n+m}$$
$$E.\ \frac{pm}{n}-\frac{pn}{m}$$
The OA is D.
Time upstream, T1 = d / m
Time downstream T2 = d / n
The total time will be, T1 + T2 = p.
Then, I just need isolate d from,
$$\frac{d}{m}+\frac{d}{n}=p\ -->d\left(\frac{n+m}{mn}\right)=p-->d=\frac{mnp}{m+n}$$
Is there a strategic approach to this question? Can any experts help, please? Thanks.
$$A.\ mnp$$
$$B.\ \frac{mn}{p}$$
$$C.\ \frac{m+n}{p}$$
$$D.\ \frac{mnp}{n+m}$$
$$E.\ \frac{pm}{n}-\frac{pn}{m}$$
The OA is D.
Time upstream, T1 = d / m
Time downstream T2 = d / n
The total time will be, T1 + T2 = p.
Then, I just need isolate d from,
$$\frac{d}{m}+\frac{d}{n}=p\ -->d\left(\frac{n+m}{mn}\right)=p-->d=\frac{mnp}{m+n}$$
Is there a strategic approach to this question? Can any experts help, please? Thanks.
