An aeroplane flies along the sides of an equilateral triangle with speed of…

2025

An aeroplane flies along the sides of an equilateral triangle with speed of 300 km/hr, 200 km/hr, 240 km/hr. The average speed of the plane while flying around the triangle is:

  1. A.

    250 km/hr

  2. B.

    290 km/hr

  3. C.

    340 km/hr

  4. D.

    240 km/hr

Attempted by 8 students.

Show answer & explanation

Correct answer: D

Step-by-Step Solution

When an object travels equal distances at different speeds, the average speed is calculated using the harmonic mean.

Identify the variables:

  • The aeroplane travels along the three sides of an equilateral triangle, meaning the distance for each segment is equal.

  • Speeds: x = 300 km/hr, y = 200 km/hr, z = 240 km/hr.

  • Apply the average speed formula for three equal distances:

    • Average Speed = (3 * x * y * z) / (xy + yz + zx)

  • Perform the calculation:

    • Numerator = 3 * 300 * 200 * 240 = 43,200,000

    • Denominator = (300 * 200) + (200 * 240) + (300 * 240)

    • Denominator = 60,000 + 48,000 + 72,000 = 180,000

    • Average Speed = 43,200,000 / 180,000 = 240 km/hr.

Explore the full course: Amcat Preparation