Solution:
To solve the problem, we can use the formula for simple interest:

Simple Interest = (Principal * Rate * Time) / 100

Where Principal is the initial amount, Rate is the interest rate, and Time is the duration of the investment.

Part 1:
Rupees 8000 become 10000 in 2 years at a simple interest.

We can use the above formula to find out the interest rate.

Simple Interest = (Principal * Rate * Time) / 100
2000 = (8000 * Rate * 2) / 100
Rate = (2000 * 100) / (8000 * 2)
Rate = 12.5%

Therefore, the interest rate is 12.5%.

Part 2:
The amount that will become rupees 6875 in 3 years at the sample rate of interest?

We can use the above formula again to find out the final amount.

Final Amount = Principal + Simple Interest
Simple Interest = (Principal * Rate * Time) / 100
Simple Interest = (6875 * 12.5 * 3) / 100
Simple Interest = 2578.125

Final Amount = 6875 + 2578.125
Final Amount = 9453.125

Therefore, the amount that will become rupees 6875 in 3 years at the sample rate of interest is rupees 9453.125.

Explanation:
- We used the formula for simple interest to find out the interest rate in the first part of the problem.
- Then, we used the same formula to find out the simple interest for the second part of the problem.
- Finally, we added the simple interest to the initial amount to get the final amount.
- The solution shows how to find out the interest rate and how to use it to calculate the final amount.