Insert three arithmetic mean (AM) between 6 and 18.

Explanation

To insert three arithmetic means (AM) between 6 and 18, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the given numbers**: We have two numbers, 6 and 18. We need to insert three arithmetic means between them.

2. **Understand the structure of the arithmetic progression (AP)**: The series will consist of five terms: the first term (T1) is 6, the second term (T2) is the first arithmetic mean (AM1), the third term (T3) is the second arithmetic mean (AM2), the fourth term (T4) is the third arithmetic mean (AM3), and the fifth term (T5) is 18.

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