In a 100 m race, Ajay runs at the speed of 4 km/h. Ajay gives Brijesh a start of 4 m and still beats him by15 s. Find the speed of Briiesh.

Answer

To solve the problem step by step, we will follow the reasoning and calculations outlined in the video transcript.

### Step 1: Understand the given information
- Ajay's speed = 4 km/h
- Distance of the race = 100 m
- Brijesh gets a start of 4 m, so he runs 96 m.
- Ajay beats Brijesh by 15 seconds.

### Step 2: Convert Ajay's speed from km/h to m/s
To convert km/h to m/s, we use the conversion factor \( \frac{5}{18} \):
\[ \text{Speed of Ajay in m/s} = 4 \times \frac{5}{18} = \frac{20}{18} = \frac{10}{9} \text{ m/s} \]

### Step 3: Calculate the time taken by Ajay to complete the race
Using the formula \( \text{Time} = \frac{\text{Distance}}{\text{Speed}} \):
\[ \text{Time taken by Ajay} = \frac{100 \text{ m}}{\frac{10}{9} \text{ m/s}} = 100 \times \frac{9}{10} = 90 \text{ seconds} \]

### Step 4: Calculate the time taken by Brijesh
Since Ajay beats Brijesh by 15 seconds, the time taken by Brijesh is:
\[ \text{Time taken by Brijesh} = 90 \text{ seconds} + 15 \text{ seconds} = 105 \text{ seconds} \]

### Step 5: Calculate Brijesh's speed
Brijesh runs 96 m in 105 seconds. To find his speed in m/s:
\[ \text{Speed of Brijesh in m/s} = \frac{96 \text{ m}}{105 \text{ s}} = \frac{96}{105} \text{ m/s} \]

### Step 6: Convert Brijesh's speed to km/h
To convert m/s to km/h, we multiply by \( \frac{18}{5} \):
\[ \text{Speed of Brijesh in km/h} = \frac{96}{105} \times \frac{18}{5} \]
Calculating this:
\[ = \frac{96 \times 18}{105 \times 5} = \frac{1728}{525} \approx 3.29 \text{ km/h} \]

### Final Answer
The speed of Brijesh is approximately **3.29 km/h**.

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