The present value of a laptop is ₹ 6561. If its value decreases every year by…

Step-by-Step Solution
To find the value of the laptop 3 years ago, we must reverse the process of annual compound depreciation.

Understand the Formula: When a value decreases by a fixed percentage (r) annually over time (n), the relationship between the initial value (P) and the present value (A) is:
A = P * (1 - r)ⁿ

Rearrange to solve for P: Since we need the initial value (P), we rearrange the formula:
P = A / (1 - r)ⁿ

Substitute the given values:

Present Value (A) = ₹ 6561

Annual Depreciation rate (r) = 10% = 0.10

Time (n) = 3 years

Calculate:

P = 6561 / (1 - 0.10)³

P = 6561 / (0.9)³

P = 6561 / 0.729

P = ₹ 9000