The ratio of the 11th term to the 18th term of an AP is `2` : `3`. Find the ratio of the 5th term to the 21st term and also the ratio of the sum of the first five terms to the sum of the first `21` terms.

Explanation

To solve the problem step by step, we will follow the instructions provided in the video transcript.

### Step 1: Understand the given information
We are given that the ratio of the 11th term to the 18th term of an arithmetic progression (AP) is 2:3. We need to find the ratio of the 5th term to the 21st term, and also the ratio of the sum of the first 5 terms to the sum of the first 21 terms.

### Step 2: Define the terms of the AP
Let:
- \( A \) = first term of the AP
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