Question 232372

Distance(d) equals Rate(r) times Time(t) or d-rt;  r=d/t and t=d/r

Approach 1:
Let t=time to separate by 510mi
By inspection, we can see that Joe and Janna are separating at the rate of 45+40 or 85 mph. So our equation to solve is:
510=85t  divide each side by t
t=6 hours-------time it takes for them to separate by 510 mi

Approach 2
Let t=time to separate by 510mi
Distance Joe travels equals 45t
Distance Janna travels equals 40t
Now we know that the above two distances must add up to 510 mi, so:
45t+40t=510
85t=510-------------------same as before


Hope this helps--ptaylor