The ratio of 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 a speed of x km/h and from B to C at a speed of 50 km/h. If his average speed for the entire journey is 40 km/h, then what is the value of (x - 20) : (x + 2)?
Answer & explanation
Correct answer: option 1
Let, distance b/w A to B is 30 km and B to C is 50 km, so total is 80 km.
AB : BC Total
Distance 3 : 5 8 Unit
Average speed = 40 km/h
Time = \(\frac{80}{40}\) = 2 hours
Total time = 2 hours (to travel A to C)
Here,
Speed to travel B to C = 50 km/hr and distance = 50 km
So, Time to travel B to C = \(\frac{50}{50}\) = 1 hour
Therefore, Time to travel from A to B = 2 - 1 = 1 hr.
⇒ Speed from A to B (x)= \(\frac{30}{1}\) = 30 km/h
⇒ x = 30
Now,
(x - 20) : (x + 2)
(30 - 20 ) : (30 + 2)
10 : 32
⇒ 5 : 16