If 15 envelope cost Rs 11.25.what is the cost of such 20 envelopes?

Answer

To solve the problem of finding the cost of 20 envelopes when 15 envelopes cost Rs. 11.25, we will use the unitary method. Here’s the step-by-step solution:

### Step 1: Find the cost of one envelope.
To find the cost of one envelope, we divide the total cost of 15 envelopes by 15.

\[ \text{Cost of 1 envelope} = \frac{\text{Total cost of 15 envelopes}}{15} = \frac{11.25}{15} \]

### Step 2: Calculate the cost of one envelope.
Now, we perform the division:

\[ \frac{11.25}{15} = 0.75 \]

So, the cost of one envelope is Rs. 0.75.

### Step 3: Find the cost of 20 envelopes.
Now that we know the cost of one envelope, we can find the cost of 20 envelopes by multiplying the cost of one envelope by 20.

\[ \text{Cost of 20 envelopes} = \text{Cost of 1 envelope} \times 20 = 0.75 \times 20 \]

### Step 4: Calculate the cost of 20 envelopes.
Now, we perform the multiplication:

\[ 0.75 \times 20 = 15 \]

Thus, the cost of 20 envelopes is Rs. 15.

### Final Answer:
The cost of 20 envelopes is Rs. 15.

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