Correct Answer - Option 1 : 30 km/h
Given:
The ratio of the speed of the bike, van and lorry = 3 ∶ 7 ∶ 5
Distance covers by lorry = 360 km
Time taken by lorry to cover = 12 hours
Concept used:
Speed = Distance/Time
Average = (Total sum)/(Total terms)
Calculations:
Let the speed of the bike, van and lorry be 3x, 7x and 5x respectively
Speed of lorry = 360/12 = 30 km/h
⇒ 5x = 30
⇒ x = 6
Speed of bike = 3x = 3 × 6 = 18
Speed of van = 7x = 7 × 6 = 42
Average speed of bike and van = (18 + 42)/2 = 30 km/h
∴ Average speed of bike and van is 30 km/h
