In what time can Saloni cover a distance of 450 m, if she runs at a speed of 20Km/hr. ?
(a)81 sec
(b)320 sec
(c)30 sec
(d)102 sec

Options

A. 81 sec
B. 320 sec
C. 3 minutes
D. 102 sec

Answer

To solve the problem, we need to find out how long it will take Saloni to cover a distance of 450 meters at a speed of 20 km/h. Here’s the step-by-step solution:

### Step 1: Convert the speed from km/h to m/s
The speed is given as 20 km/h. To convert this to meters per second (m/s), we use the conversion factor:
\[ 1 \text{ km/h} = \frac{5}{18} \text{ m/s} \]
So, we calculate:
\[ 20 \text{ km/h} = 20 \times \frac{5}{18} \text{ m/s} = \frac{100}{18} \text{ m/s} \approx 5.56 \text{ m/s} \]

### Step 2: Use the formula for time
The formula to calculate time when distance and speed are known is:
\[ \text{Time} = \frac{\text{Distance}}{\text{Speed}} \]
We have the distance as 450 meters and the speed as approximately 5.56 m/s. Now we can substitute these values into the formula:
\[ \text{Time} = \frac{450 \text{ m}}{5.56 \text{ m/s}} \approx 81 \text{ seconds} \]

### Step 3: Conclusion
Thus, the time taken by Saloni to cover a distance of 450 meters at a speed of 20 km/h is approximately 81 seconds.

### Final Answer
The correct option is (a) 81 seconds.

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