+0  
 
0
51
2
avatar

For travel from Washington DC to Baltimore by car, a constant speed of 60 mph was maintained.  For the return trip, there was a constant speed of 40 mph. What was the average speed over the whole two-way trip?

 Nov 28, 2020
 #1
avatar
0

You have to give either the distance between Washigton and Baltimore, or the time it took them to drive back and forth in order to calculate the average speed.

 Nov 28, 2020
 #2
avatar
0

d = distance = rate * time

d is the same for each leg of the trip....out and back

 

60 * t1   =   40 * t2       divide both sides by 60

t1 = 2/3 t2

 

60 * t1   +    40 * t2   = a (t1 + t2)                      sub in    t1 = 2/3 t2

60 (2/3 t2)   +   40 t2   = a (2/3 t2 + t2)              divide both sides by   t2

40 + 40 = 5/3 a

a = 48 m/hr

 Nov 28, 2020

55 Online Users

avatar