A postman riding a bicycle at 15 km/h can reach a village in 4 hours. If he is delayed by 1 hour at the start, then in order to reach his destination in time, he should ride with a speed of :

Options

A. 20 km/h
B. 16 km/h
C. 14 km/h
D. 12 km/h

Answer

To solve the problem, we need to determine the speed at which the postman must ride to reach the village on time after a 1-hour delay. Here’s a step-by-step solution:

### Step 1: Calculate the distance to the village
The postman rides at a speed of 15 km/h for 4 hours.

\[ \text{Distance} = \text{Speed} \times \text{Time} = 15 \text{ km/h} \times 4 \text{ h} = 60 \text{ km} \]

### Step 2: Determine the total time available after the delay
Since the postman is delayed by 1 hour, he has 4 hours - 1 hour = 3 hours left to reach the village on time.

### Step 3: Calculate the required speed to cover the distance in the remaining time
To find the speed needed to cover the distance of 60 km in 3 hours, we use the formula:

\[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} = \frac{60 \text{ km}}{3 \text{ h}} = 20 \text{ km/h} \]

### Conclusion
Therefore, the postman should ride at a speed of **20 km/h** to reach his destination on time.

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