Question

A train goes from New Orleans to Boston at 40 mph. On the way back it returns with a speed 80 mph. If it takes it an hour less time to return, what is its average speed?

Answer 1

Yes, it would be 53.33 miles per hour!

Answer 2

Distance from New Orleans to Boston and back is the same.

t - time from New Orleans to Boston

(t-1) - time from Boston to New Orleans

40t - distance between New Orleans and Boston.

80(t-1) - distance between Boston and New Orleans.

40t = 80(t-1)

40t = 80t - 80

40t = 80

t=2 h

To find average speed we need to find all distance and divide it at all time.

All distance = 40t +80(t-1) = 120t - 80

All time = t+(t-1)= 2t-1

Average speed =(120t - 80)/(2t-1)

Now we can substitute t=2.

Average speed =(120*2 - 80)/(2*2-1)=53.33 m/s