DSNL charges a fixed rental of ₹ 350 per month. It allows 200 calls free per month. Each call is charged at ₹ 1.4 when the number of calls exceeds 200 per month and it charges ₹ When the number of calls exceeds 400 per month and so on. A customer made 150 calls in February and 250 calls pin March. By how much per cent the each call is cheaper in ,March than each call in February?

Options

A. `28%`
B. `25%`
C. `18.5%`
D. None of the above

Answer

To find out by how much percent each call is cheaper in March than each call in February, we will follow these steps:

### Step 1: Calculate the total cost for February
In February, the customer made 150 calls.
- Fixed rental: ₹350
- Since the number of calls (150) is less than 200, there are no extra charges.

**Total cost in February = Fixed rental = ₹350**

### Step 2: Calculate the cost per call in February
To find the cost per call in February, we divide the total cost by the number of calls made.

\[ \text{Cost per call in February} = \frac{\text{Total cost in February}}{\text{Number of calls in February}} = \frac{350}{150} \approx 2.33 \]

### Step 3: Calculate the total cost for March
In March, the customer made 250 calls.
- Fixed rental: ₹350
- Free calls allowed: 200
- Extra calls made: 250 - 200 = 50 calls
- Charge for extra calls: 50 calls × ₹1.4 = ₹70

**Total cost in March = Fixed rental + Charge for extra calls = ₹350 + ₹70 = ₹420**

### Step 4: Calculate the cost per call in March
To find the cost per call in March, we divide the total cost by the number of calls made.

\[ \text{Cost per call in March} = \frac{\text{Total cost in March}}{\text{Number of calls in March}} = \frac{420}{250} = 1.68 \]

### Step 5: Calculate the percentage decrease in cost per call
Now, we need to find the percentage decrease in cost per call from February to March.

\[ \text{Decrease in cost per call} = \text{Cost per call in February} - \text{Cost per call in March} = 2.33 - 1.68 = 0.65 \]

Now, we will calculate the percentage decrease:

\[ \text{Percentage decrease} = \left( \frac{\text{Decrease in cost per call}}{\text{Cost per call in February}} \right) \times 100 = \left( \frac{0.65}{2.33} \right) \times 100 \approx 27.9\% \]

### Final Answer
The cost per call in March is approximately **27.9% cheaper** than in February.

---