A car covers its journey at the speed of 80km/hr in 10hours. If the same distance is to be covered in 4 hours, by how much the speed of car will have to increase ?

Options

A. 40km/hr
B. 60km/hr
C. 90km/hr
D. 120km/hr

Answer

To solve the problem step by step, we need to determine the distance covered by the car and then find the required speed to cover that distance in a shorter time. Finally, we will calculate the increase in speed.

### Step 1: Calculate the distance covered by the car.
The formula to calculate distance is:
\[ \text{Distance} = \text{Speed} \times \text{Time} \]

Given:
- Speed = 80 km/hr
- Time = 10 hours

So, the distance covered by the car is:
\[ \text{Distance} = 80 \, \text{km/hr} \times 10 \, \text{hours} = 800 \, \text{km} \]

### Step 2: Calculate the speed required to cover the same distance in 4 hours.
We need to find the speed required to cover the same distance of 800 km in 4 hours.

Using the formula:
\[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} \]

Substituting the values:
\[ \text{Speed} = \frac{800 \, \text{km}}{4 \, \text{hours}} = 200 \, \text{km/hr} \]

### Step 3: Calculate the increase in speed.
Now, we need to find out how much the speed needs to increase from the original speed of 80 km/hr to the new speed of 200 km/hr.

Increase in speed is calculated as:
\[ \text{Increase in Speed} = \text{New Speed} - \text{Original Speed} \]
\[ \text{Increase in Speed} = 200 \, \text{km/hr} - 80 \, \text{km/hr} = 120 \, \text{km/hr} \]

### Final Answer:
The speed of the car will have to increase by **120 km/hr**.

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