Question

6. It takes a delivery truck 2 hours to travel 70 km to deliver a new fridge. The truck drives part of

the way on the highway at 80 km/h and the rest on city roads in traffic at only 20 km/h. (6 marksT)
a) How far did the truck travel on each road?
4

Answer 1

40 km on the highway

30 km on the city roads

Explanation:

Let x = highway

Let y = city road

The time formula: time = distance / speed.

1) Since we do not know the distance travelled on the highway and city roads but we do know the total time taken, we can say x + y = 70. Set the distances x and y and all equated to 2 hours, since we do not know them, nor do we know the time. This is called a system of equations.

x + y = 70

x/80 + y/20 = 2

2) Solve the system of equations using substitution.

x = 70 - y

---------------

70 - y/80 + y/20 = 2

70 + 3y/80 = 2

y = 30

---------------------------------

x + 30 = 70

x = 70 - 30

x = 40

Therefore, the delivery truck travelled 40 km on the highway and 30 km on the city roads.