An scooterist travels at 36 km/hr for 5 hours and at 45 km/hr for 4 hours .Find his average speed for the whole journey .

Answer

To find the average speed of the scooterist for the entire journey, we can use two methods: the formula for average speed based on distances and speeds, and the formula based on total distance and total time.

### Step-by-Step Solution:

**Step 1: Calculate the distance traveled at each speed.**

- The scooterist travels at 36 km/hr for 5 hours.

\[ \text{Distance}_1 = \text{Speed} \times \text{Time} = 36 \, \text{km/hr} \times 5 \, \text{hr} = 180 \, \text{km} \]

- The scooterist travels at 45 km/hr for 4 hours.

\[ \text{Distance}_2 = \text{Speed} \times \text{Time} = 45 \, \text{km/hr} \times 4 \, \text{hr} = 180 \, \text{km} \]

**Step 2: Calculate the total distance traveled.**

\[ \text{Total Distance} = \text{Distance}_1 + \text{Distance}_2 = 180 \, \text{km} + 180 \, \text{km} = 360 \, \text{km} \]

**Step 3: Calculate the total time taken.**

\[ \text{Total Time} = 5 \, \text{hr} + 4 \, \text{hr} = 9 \, \text{hr} \]

**Step 4: Calculate the average speed.**

Using the formula for average speed:

\[ \text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}} = \frac{360 \, \text{km}}{9 \, \text{hr}} = 40 \, \text{km/hr} \]

### Final Answer:

The average speed of the scooterist for the whole journey is **40 km/hr**.

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