A boat's speed in still water is 45 km/h, while the river is flowing at a speed of 15 km/h. The time taken to cover a certain distance upstream is 9 h more than the time taken to cover the same distance downstream. Find the distance (in km).

Question

Question

This question was previously asked in

SSC CGL 2023 Tier-I Official Paper (Held On: 20 Jul 2023 Shift 4)

Answer 1

GIVEN:

Difference in time = 9 hours

A boat's speed in still water = 45 km/h

Stream speed = 15 km /h

FORMULA USED:

Distance = Speed × Time

Speed in upstream = (still water's speed - stream speed)

Speed in downstream = (still water speed + stream speed )

CALCULATION:

Here, still water speed = 45 km/h , stream speed = 15 km/h

Upstream speed = (45 - 15) = 30 km/h, Downstream speed = (45 + 15) = 60 km/h.

According to the given question,

The time taken to cover the Upstream distance is 9 hours more than the Downstream

Now, let the required distance be d then,

⇒ d/30 - d/60 = 9

⇒ (2d - d)/60 = 9

⇒ d = 9 × 60 = 540

Hence, the required distance is 540 km.