Question 143652
Imagine you have a stopwatch. Start the stopwatch the instant
the 2nd friend leaves. Then ask: "where is the 1st one at that time?"
He has gone {{{60*2 = 120}}}mi
When will they pass eachother?
Call the distance the 1st one has to go {{{d}}}
Then the distance the 2nd one has to go will be {{{d + 120}}}
The stopwatch will show the same time for both when they meet
{{{d/t = 60}}} for 1st friend
{{{(d + 120)/t = 80}}} for 2nd friend
-------------------------------------
{{{d/t = 60}}}
{{{d = 60t}}}
{{{(60t + 120)/t = 80}}}
{{{60t + 120 = 80t}}}
{{{20t = 120}}}
{{{t = 6}}}hrs
They will meet in 6 hours
check:
{{{d/t = 60}}}
{{{d/6 = 120}}}
{{{d = 720}}}
{{{(60t + 120)/t = 80}}}
{{{(60*6 + 120)/6 = 80}}}
{{{360 + 120 = 480}}}
{{{480 = 480}}}
OK