Question

An aeroplane flies with an average speed of 756 km/h. A helicopter takes 48 h to cover twice the distance covered by aeroplane in 9 h. How much distance will the helicopter cover in 18 h? (Assuming that flights are non-stop and moving with uniform speed.)

• A. 5010km
• B. 4875km
• C. 5760km
• D. 5103km

Hint:

Find the helicopter's total distance in 48 hours, then scale it down proportionally to 18 hours.

Answer 1

The Correct Option is D

Step 1: Find the helicopter's total distance for the 48-hour trip.
Aeroplane distance in 9 hours $= 756 \times 9 = 6804$ km, and the helicopter covers twice this in 48 hours, so its 48-hour distance is $2 \times 6804 = 13608$ km.

Step 2: Scale this distance down to 18 hours using a direct proportion, without finding the speed first.
Since the helicopter moves at a uniform speed, distance is proportional to time: $\frac{\text{distance in 18 h}}{\text{distance in 48 h}} = \frac{18}{48} = \frac{3}{8}$.

Final Answer:
Distance in 18 hours $= 13608 \times \frac{3}{8} = 5103$ km. \[ \boxed{5103 \text{ km}} \]