The ratio of the distance between two places A and B to the distance between places B and C is 3 : 5. A man travels from A to B at 30 km/h and from B to C at x km/h. If his average speed for the entire journey is 40 km/h, then what is the value of (x - 7) (in km/h)?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 43.
Let AB = 3 km, BC = 5 km
8/(3/30 + 5/x) = 40
⇒ (0.1 + 5/x) = 1/5 = 0.2
⇒ 0.1 = 5/x
⇒ x = 5/0.1 = 50 km/h
⇒ x - 7 = 50 - 7 = 43 km/h