Question 151564
You can use the distance formula for this problem:
{{{d[1] = r[1]*t}}} and
{{{d[2] = r[2]*t}}} where d = distance traveled, r = rate (speed) of travel, and t = time of travel.
For the first truck, r = 65 mph and we have to find t.
For the second truck, r = 55 mph and we have to find t but this will be the same value as for the first truck, and the sum of the distances traveled by the two trucks will be {{{d[1]+d[2] = 936}}}miles.
{{{d[1] = 65*t}}}
{{{d[2] = 55*t}}}
{{{d[1]+d[2] = 936}}} Substitute the d's from the above equations.
{{{65*t+55*t = 936}}}
{{{120*t = 936}}} Divide both sides by 120.
{{{t = 7.8}}}
It will take 7.8 hours (that's 7 hours and 48 minutes) for the trucks to be 936 miles apart.