Beena bought m pencils at n paise each. How much change did she get back, if she paid Rs 20 ?

Options

A. `Rs(20 - (mn)/(100))`
B. Rs (2 - m -n)
C. Rs (200 - m - n)
D. `Rs (200 - (mn)/(100))`

Answer

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

### Step 1: Understand the Problem
Beena bought \( m \) pencils at \( n \) paise each. She paid Rs 20. We need to find out how much change she received after her purchase.

### Step 2: Convert the Payment to Paise
Since the cost of the pencils is given in paise, we should convert Rs 20 into paise.
1 Rupee = 100 paise, so:
\[ 20 \text{ Rs} = 20 \times 100 = 2000 \text{ paise} \]

### Step 3: Calculate the Total Cost of the Pencils
The cost of one pencil is \( n \) paise. Therefore, the cost of \( m \) pencils is:
\[ \text{Total Cost} = m \times n \text{ paise} \]

### Step 4: Calculate the Change Received
To find out how much change Beena received, we subtract the total cost of the pencils from the amount she paid (in paise):
\[ \text{Change} = \text{Amount Paid} - \text{Total Cost} \]
Substituting the values we have:
\[ \text{Change} = 2000 \text{ paise} - (m \times n) \text{ paise} \]
This simplifies to:
\[ \text{Change} = 2000 - mn \text{ paise} \]

### Step 5: Final Answer
Thus, the change Beena received after buying the pencils is:
\[ \text{Change} = 2000 - mn \text{ paise} \]