The fourth, seventh, and the last term of a G.P. are 10, 80, and 2560, respectively. Find the first term and the number of terms in G.P.

Explanation

To solve the problem step by step, we will first define the terms of the geometric progression (G.P.) and then use the given information to find the first term and the number of terms.

### Step 1: Define the variables
Let:
- \( a \) = first term of the G.P.
- \( r \) = common ratio of the G.P.

### Step 2: Write the equations for the given terms
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