In the following question, two statements are numbered as A and B. On solving these statements we get quantities A and B respectively. Solve for both quantities and chose the correct option. Quantity A: A man takes 11/9 times downstream time to row upstream keeping the distance same in both cases. What is the speed of boat (m/s) in still water if it takes 6 hours to travel 80 km in downstream? Quantity B: A boat running in upstream covers 20 km distance in 3 hours while covering the same distance in downstream it takes 2 hours. What is the speed of the boat in still water (m/s)? Correct Answer Quantity A > Quantity B Solving for Quantity A - Distance cover = 80 km Time taken = 6 hours Speed of downstream = 80/6 = 13.33 kmph Speed of downstream = Speed of boat + speed of stream ---- (I) Speed of upstream = speed of boat - speed of stream ---- (II) Let assume Speed of boat as x kmph , Speed of stream as y kmph, Time taken in upstream is 11/9 times more, Time taken in upstream = (11/9) × 6 = 7.33 hours Speed of upstream = 80/7.33 = 10.91 kmph Substitute the values in Eq (I) and Eq (II); ⇒ x + y = 13.33 ⇒ x - y = 10.91 By eliminating y terms in above equation, ⇒ 2x = 24.24 ⇒ x = 12.12 kmph Convert the vale in m/s by multiplying it 18/5, Speed of boat = 12.12 × (5/18) = 3.36 m/s Solving for Quantity B - Let assume speed of boat in still water = x kmph Speed of stream = y kmph For the speed of boat in upstream, Distance covered = 20 km Time taken = 3 hour Speed of boat in upstream = 20/3 = 6.67 kmph For the speed of boat in downstream, Distance covered = 20 km Time taken = 2 hour Speed of boat in downstream = 20/2 = 10 kmph Speed of downstream = Speed of boat + speed of stream = x + y = 10 Speed of upstream = speed of boat - speed of stream = x - y = 6.67 By eliminating y terms, ⇒ 2x = 16.67 ⇒ x = 8.335 kmph Convert the value in m/s by multiplying 5/18, ⇒ x = 8.335 × (5/18) = 2.315 m/s ∴ Quantity A > Quantity B