A sum of money doubles itself in 20 years. In how many years will it become four times?

Explanation

To solve the problem step by step, we will use the concept of Simple Interest (SI) and the relationship between Principal (P), Rate (R), Time (T), and Amount (A).

### Step 1: Understand the Problem
We know that a sum of money doubles in 20 years. We need to find out how many years it will take for the same sum to become four times.

### Step 2: Define the Principal
Let's assume the principal amount (P) is ₹100.

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