Explanation:

- Let's denote the original cost price as \( C \).

- The original selling price is \( C + 0.25C = 1.25C \).

- If both prices are increased by Rs200, the new selling price is \( 1.25C + 200 \) and the new cost price is \( C + 200 \).

- The new profit percentage is given as 20%, so:

$$

\frac{(1.25C + 200) - (C + 200)}{C + 200} \times 100 = 20

$$

- This simplifies to:

$$

\frac{0.25C}{C + 200} \times 100 = 20

$$

- Solving this equation:

$$

\frac{0.25C}{C + 200} = 0.2

$$

$$

0.25C = 0.2(C + 200)

$$

$$

0.25C = 0.2C + 40

$$

$$

0.05C = 40

$$

$$

C = 800

$$

- Rs800 is indeed the correct original cost price.