worded problem

[Wingfooted]

I've been having trouble solving this problem and don't understand how to get to the answer, any help appreciated. (Solution even more appreciated)

"A man rows upstream at 3km/h and back to the same place at 5km/h; he takes 48 minutes all together. How far upstream did he go? "

Ans: 1.5km

[Baltuilhe]

Good afternoon!

The same distance d was walked both ways.
To go, time [tex]t_1[/tex].
To return, time [tex]t_2[/tex].
Summing both times, 48min, right?
Converting to hour:
[tex]\dfrac{48}{60}=0,8=\dfrac{8}{10}=\dfrac{4}{5}[/tex]

Definition of speed:
[tex]v=\dfrac{d}{t}\\\\t=\dfrac{d}{v}[/tex]

Given data:
[tex]v_1=3\\v_2=5[/tex]

Using this equation:
[tex]t_1+t_2=\dfrac{4}{5}\\\\\\\dfrac{d}{3}+\dfrac{d}{5}=\dfrac{4}{5}\\\\\\\dfrac{5d+3d}{15}=\dfrac{12}{15}\\\\\\8d=12\\\\\\d=\dfrac{12}{8}=1,5[/tex]

So, 1,5km is the answer!

I hope I have helped!