Question

A car travels a distance in the form of an equilateral triangle with the speed of 40 km per hr, 60 km per hr, and 80 km per hr respectively. Find the time taken by car at average speed for 1440 km distance.

1. 26 hr.
2. 36 hr.
3. 24 hr.
4. 25 hr.

Answer 1

Correct Answer - Option 1 : 26 hr.

Given

Car speed is given side₁ = 40 km per hr

Car speed is given side₂ = 60 km per hr

Car speed is given side₃ = 80 kmr per hr

As distance are covered along three sides (equal) of a triangle

Average speed

The average speed of the car At three side (equal) = 

 ⇒  \(\frac{3}{{\frac{1}{{40}} + \frac{1}{{60}} + \frac{1}{{80}}}}\)

⇒  \(\frac{3}{{\frac{{6 + 4 + 3}}{{240}}}}\)

⇒ \(\frac{{3 \times 240}}{{13}}\)

Distance (1440 km) covered at average speed = \(\frac{{1440}}{{720}} \times 13\) 

= 26 hr