Dipesh writes letters to four of his friends. He asks each of them to copy the letter and mail to four different persons with the request that they continue the chain similarly. Assuming that the chain is not broken and that it costs 25 paise to mail one letter, find the total money spent on postage till the 8th set of letters is mailed.

Explanation

To solve the problem step by step, we will analyze the situation and calculate the total money spent on postage until the 8th set of letters is mailed.

### Step 1: Identify the pattern of letter sending
Dipesh sends letters to 4 friends. Each of these friends sends letters to 4 new people. This creates a pattern where each set of letters is multiplied by 4.

- **1st set:** 4 letters (sent by Dipesh)
- **2nd set:** Each of the 4 friends sends 4 letters, so \(4 \times 4 = 16\) letters
- **3rd set:** Each of the 16 people sends 4 letters, so \(16 \times 4 = 64\) letters
...