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 these instructions:

### Step 1: Understand the given information
We know that the ratio of the 11th term to the 18th term of an arithmetic progression (AP) is given as \(2:3\).

### Step 2: Write the formula for the nth term of an AP
The nth term of an AP can be expressed as:
\[
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