A mobile bill costs Rs. 10 for 3 minute 30 seconds. What is the cost in rupees for 4 minutes 10 seconds. (rounded to one decimal).
A. 11.9
B. 12
C. 11.8
D. 11.7

Options

A. A
B. C
C. B
D. D

Answer

To solve the problem step by step, we will first convert the given times into seconds, then determine the cost per second, and finally calculate the cost for the required time.

### Step 1: Convert the time from minutes and seconds to seconds
- For 3 minutes 30 seconds:
- 3 minutes = 3 × 60 = 180 seconds
- Total = 180 seconds + 30 seconds = 210 seconds

- For 4 minutes 10 seconds:
- 4 minutes = 4 × 60 = 240 seconds
- Total = 240 seconds + 10 seconds = 250 seconds

### Step 2: Determine the cost per second
- The cost for 210 seconds is Rs. 10.
- Cost per second = Total cost / Total seconds
\[ \text{Cost per second} = \frac{10 \text{ Rs}}{210 \text{ seconds}} = \frac{10}{210} \text{ Rs/second} = \frac{1}{21} \text{ Rs/second} \]

### Step 3: Calculate the cost for 250 seconds
- Cost for 250 seconds = Cost per second × Total seconds
\[ \text{Cost for 250 seconds} = \frac{1}{21} \text{ Rs/second} \times 250 \text{ seconds} = \frac{250}{21} \text{ Rs} \]

### Step 4: Calculate the value of \(\frac{250}{21}\)
- Performing the division:
\[ \frac{250}{21} \approx 11.90476 \]

### Step 5: Round the result to one decimal place
- Rounding 11.90476 to one decimal place gives us 11.9.

### Conclusion
Thus, the cost for 4 minutes 10 seconds is approximately Rs. 11.9.

### Answer
The correct option is **A. 11.9**.

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