Subject: General Aptitude · Chapter: Time and Distance · Exam: · Marks: · Difficulty:
A distance of 425 km separates two trains moving towards each other at a speed of 200 km/hr each. What will be the distance between them after 1 hr 30 min, if they reduce their speed by half, every half an hour?
(a)75 km
(b)120 km
(c)150 km
(d)200 km
Answer
Answer (as printed): A
Explanation
Relative speed = (200 + 200) km/hr = 400 km/hr. Distance covered in 1 hr 30 min $=\left(400\times\frac{1}{2}+200\times\frac{1}{2}+100\times\frac{1}{2}\right)$ km $=(200+100+50)$ km $=350$ km. [speed reduces by half every half an hour] Hence, distance between the trains $=(425-350)$ km $=75$ km.
Explanation as extracted from the printed page; notation may be imperfect.