A telephone bill costs Rs 35.50 for 3 minutes 20 seconds. What is the cost, in rupees, for 5 minutes 30 seconds? (Round up to one decimal).

Options

A. 58.6
B. `58.7`
C. 58.5
D. 58.8

Answer

To solve the problem, we need to find the cost of a telephone bill for 5 minutes and 30 seconds based on the given cost for 3 minutes and 20 seconds. Here’s a step-by-step solution:

### Step 1: Convert the given time into seconds
First, we need to convert both the given time (3 minutes and 20 seconds) and the time we want to calculate (5 minutes and 30 seconds) into seconds.

- **For 3 minutes and 20 seconds:**
\[ 3 \text{ minutes} = 3 \times 60 = 180 \text{ seconds} \]
\[ 20 \text{ seconds} = 20 \text{ seconds} \]
\[ \text{Total time in seconds} = 180 + 20 = 200 \text{ seconds} \]

- **For 5 minutes and 30 seconds:**
\[ 5 \text{ minutes} = 5 \times 60 = 300 \text{ seconds} \]
\[ 30 \text{ seconds} = 30 \text{ seconds} \]
\[ \text{Total time in seconds} = 300 + 30 = 330 \text{ seconds} \]

### Step 2: Find the cost per second
Now that we have the total time in seconds for both cases, we can find the cost per second.

- The cost for 200 seconds is Rs 35.50.
- To find the cost per second:
\[ \text{Cost per second} = \frac{35.50}{200} = 0.1775 \text{ Rs/second} \]

### Step 3: Calculate the cost for 330 seconds
Next, we will calculate the cost for 330 seconds using the cost per second we just calculated.

- The cost for 330 seconds is:
\[ \text{Cost for 330 seconds} = 0.1775 \times 330 \]
\[ = 58.575 \text{ Rs} \]

### Step 4: Round the answer to one decimal place
Finally, we need to round the answer to one decimal place.

- Rounding 58.575 to one decimal place gives us:
\[ 58.6 \text{ Rs} \]

### Final Answer
The cost for 5 minutes and 30 seconds is **Rs 58.6**.

---