What time does the second car catch the first car?

Question

A car going 39 mph leaves at 9 a.m. on very long trip. A second car going 63 mph leaves at 11 a.m. following the first car. At what time does second car catch the first 

Answer 1

This is a D-I-R-T (Distance-Is-Rate-times-Time) problem.   [D=RT]

 

When the second car “catches” the first, the distance traveled by the two cars is the same.

 

Let T=0 when the first car starts.

      The second car starts at T=2.

Find the value of T when the cars meet.

 

Distance:             First Car                             Second Car

                       (39 mph)*(T)          =         (63)*(T-2)

 

The math:

      39T = 63T -126

     126 + 39T = 63T        [add 126 to both sides]

      126 = 24T                 [subtract 39T from both sides]

     T = 5  1/4 hours

 

The second car “catches” the first at 2:15 p.m.