Question

Ratio of the speed of a boat  to a stream is 8 ∶ 5. Distance travelled upstream in 5.5 hours is 33 km. What will be the downstream speed(in km/hr) if the speed of the boat is 50% more than previous speed?

1. 26
2. 29
3. 31
4. 34
5. 37

Answer 1

Correct Answer - Option 4 : 34

Given:

Time to travel 33 km upstream = 5.5 hours

Ratio of the speed of the boat to the speed of the stream = 8 ∶ 5

Formula used:

Speed = Distance/Time

Downstream speed = u + v

Upstream speed = u – v

u and v are boat and stream speeds

Calculation:

Let the speed of the boat to the speed of the stream be 8x and 5x respectively

Upstream speed = 33/5.5 km/hr

⇒ 6 km/hr

Now, 

⇒ 8x – 5x = 6

⇒ 3x = 6

⇒ x = 2

Boat speed = 8x = 16 km/hr

Stream speed = 5x = 10 km/hr

New boat speed = 16 × (100 + 50)% = 24 km/hr

Downstream speed = 24 + 10 = 34 km/hr

∴ The downstream speed is 34 km/hr