Question 1122780
<pre>
                     SPEED       TIME         DISTANCE
S to P               r           700/r           700
P to S               r+30        700/(r+30)      700
TOTAL                             20
</pre>

{{{highlight_green(700/r+700/(r+30)=20)}}}-----equation to solve, first for r.


The AVERGAE speed for the whole journey is  {{{1400/20=70}}}, kilometers per hour.