Question

A motor car does a journey in 17.5 hours, covering the first half at 30 km/h and the second half at 40 km/h. find the distance of the journey

Answer 1

Let distance of the journey be 2x.
Time taken to cover first half=x/30.
Time taken to cover second half=x/40
Total time =x/30+x/40=17.5
LCM=120
(4x+3x)/120=17.5
7x=17.5*120
x=17.5*120/7
x=300km

Answer 2

The total distance of the journey is 612.5 km

Given data :

Speed of the first half = 30km/h

Speed of the second half = 40km/h

Total time = 17.5 hours

So,

The time of two halves of the journey is = (17.5/2) = 8.75 hours

So,

In the first half the car covers

1 hour = 30 km

8.75 hours = 30×8.75 = 262.5 km

In the second half the car covers

1 hour = 40 km

8.75 hours = 40×8.75 = 350 km

Total distance = (262.5+350) = 612.5 km (answer)