Question

Time taken by a boat in upstream is twice of the downstream. Find the ratio between the speed of the boat in still water and the speed of the current.
1. 1 ∶ 3
2. 1 ∶ 2
3. 3 ∶ 1
4. 2 ∶ 1
5. 3 ∶ 2

Answer 1

Correct Answer - Option 3 : 3 ∶ 1

Given:

The boat takes twice the time in upstream than downstream.

Formula used:

Distance = Speed × Time

Speed in upstream = (Speed in still water - speed of current)

Speed in downstream = (Speed in still water + speed of current)

Calculation:

Let the speed in still water be x km/h and the speed of current be y km/h

So, Speed in upstream = (x - y) km/h

Speed in downstream = (x + y) km/h

Let the time taken by boat in upstream and downstream be 2t and t respectively.

So, (x - y) × 2t = (x + y) × t

⇒ 2x - 2y = x + y

⇒ x = 3y

⇒ x/y = 3/1

⇒ x ∶ y = 3 ∶ 1

∴ The ratio between the speed of the boat in still water and the speed of the current is 3 ∶ 1