A man went downstream for 28 km in a motor boat and immediately returned. It took the man twice as long to make the return trip. If the speed of the river flow were twice as high, the trip downstream and back would take 672 minutes. Find the speed of the boat in still water and the speed of the river flow.
A) 12 km/hr, 3 km/hr B) 9 km/hr, 3 km/hr
C) 8 km/hr, 2 km/hr D) 9 km/hr, 6 km/hr
A motorboat went downstream for 28 km
Answer: B) 9 km/hr, 3 km/hr
Let the speed of the boat = p kmph
Let the speed of the river flow = q kmph
From the given data,
2 x 28p + q = 28p − q
=> 56p – 56q -28p – 28q = 0
=> 28p = 84q
=> p = 3q.
Now, given that if
283q + 2q + 283q − 2q = 67260=> 285q + 28q = 67260=> q = 3 kmph=> x =3q = 9 kmph
Hence, the speed of the boat = p kmph = 9 kmph and the speed of the river flow = q kmph = 3 kmph.
Subject: Boats and Streams – Quantitative Aptitude – Arithmetic Ability
Exam Prep: AIEEE , Bank Exams , CAT , GATE
Job Role: Analyst , Bank Clerk , Bank PO