A car completes a journey in 18 h covering the first half of the journey at a speed of 40 km/h and the second half of the journey at a speed of 50 km/h. Find the distance of the journey.

Correct option is A

Given:

Total time = 18 hours

First half of the journey at 40 km/h

Second half at 50 km/h

Formula Used:
Time = Distance ÷ Speed
Total time = time for first half + time for second half

Solution:

Let total distance = 2x, so each half = x

Now,

​$$\frac{x}{40} + \frac{x}{50} = 18\\ \ \\ \frac{5x + 4x}{200} = 18 \\ \ \\ \frac{9x}{200} = 18 \\ \ \\ 9x = 3600 \\ \ \\ x = 400$$​​

Total distance = 2x = $$2 \times 400$$​ = 800 km