A truck travels at 90 km/hr for the first `1(1)/(2)` hours. After that it travels at 70 km/hr. Find the time taken by the truck to travel 310 kilometres

Options

A. 2.5 hrs
B. 3 hrs
C. 3.5 hrs
D. 4 hrs

Answer

To solve the problem step by step, let's break it down:

### Step 1: Calculate the distance traveled in the first 1.5 hours at 90 km/hr.
- **Formula**: Distance = Speed × Time
- **Calculation**:
\[ \text{Distance} = 90 \text{ km/hr} \times 1.5 \text{ hr} = 135 \text{ km} \]

### Step 2: Determine the remaining distance to be traveled.
- **Total distance**: 310 km
- **Distance already traveled**: 135 km
- **Remaining distance**:
\[ \text{Remaining Distance} = 310 \text{ km} - 135 \text{ km} = 175 \text{ km} \]

### Step 3: Calculate the time taken to travel the remaining distance at 70 km/hr.
- **Formula**: Time = Distance / Speed
- **Calculation**:
\[ \text{Time} = \frac{175 \text{ km}}{70 \text{ km/hr}} = 2.5 \text{ hr} \]

### Step 4: Calculate the total time taken for the journey.
- **Total time**:
\[ \text{Total Time} = \text{Time at 90 km/hr} + \text{Time at 70 km/hr} \]
- **Calculation**:
\[ \text{Total Time} = 1.5 \text{ hr} + 2.5 \text{ hr} = 4 \text{ hr} \]

### Final Answer:
The total time taken by the truck to travel 310 kilometers is **4 hours**.

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