Question

You are driving home from school steadily at 91 km/h for 160 km . It then begins to rain and you slow to 64 km/h instantly. You arrive home after driving 4.0 hours.How far is your hometown from school?

Answer 1

Total distance = (average speed) x (total time)

What do we know, and what else can we figure out ?

-- Total time = 4 hours.

-- First piece of the trip:

. . . distance . . . 160 km

. . . speed . . . 91 km/h.  

. . . time . . . (160 km) / (91 km/hr) = 1.758 hours

-- Second piece of the trip:

. . . speed . . . 64 km/h

. . . time . . . (4 - 1.758) = 2.242 hours

. . . distance (64 km) x (2.242 hr) = 143.47 km

What we're trying to find is the total distance.  Looking back over our work for the two pieces of the trip, we see that we have the distance for each piece now, so all we have to do is addummup.

Total distance = (160 km) + (143.47 km)

Total distance = 303.47 km