Correct Answer - Option 2 : 18
Given
The car can finish a certain journey in 10 hours at the speed of 42 kmph
Formula used
Speed = Distance/Time
Calculation
Total distance covered by car = 10 × 42 = 420 km
Next, the distance should be covered in 7 hours
⇒ New speed = 420/7 = 60 km/hr
∴ Speed of car must be increase by (60 - 42) = 18 km/hr