Question

A car travels with speed of 30 km per hour for 30 minutes and then with speed of 40 km per hour for 1 hour:

a) find the total distance travelled by the car

b) find the total time of travel

Please explain me all this concept very clearly

Answer 1

Recall the distance formula:

Distance = speed x time

In this problem the car has two different parts of its journey.
First part:
"A car travels at 30 km/h for 30 minutes"
D₁ = 30 km/hr x 30 min (we need time to be in hours)
D₁ = 30 km/hr x 30/60 hr (now we can multiply)
D₁ = 15 km (this is the distance of the first part)

Second part:
"and then at 40 km/h for 1 hour or 60 minutes."

D₂ = 40 km/hr x 60min (we need time to be in hours)
D₂ = 40 km/hr x 60/60 hr (now we can multiply)
D₂ = 40 km (this is the distance of the second part)

What is the total distance traveled?
D_total = D₁ + D₂ = 15 km + 40 km = 55 km

The total distance traveled is 15 km.

To find the total time taken
time taken to travel a distance 15 km at 30 km/hr, t1 = 30 min (given in question)= 0.5 hr
time taken to travel a distance 40 km at 40km/hr , t2 =1 hr
therefore total time taken =t1+t2
=0.5+1
=1.5 hr