Step-by-step explanation:
Let \( \text{Cost Price (CP)} \) be the cost price of the tube light.
The selling price (\( \text{Selling Price (SP)} \)) is given by the formula:
\[ SP = CP + \text{Profit} \]
In this case, the profit is 20% of the cost price:
\[ \text{Profit} = 0.20 \times CP \]
The selling price is given as Rs 240:
\[ 240 = CP + 0.20 \times CP \]
Now, solve for \( CP \):
\[ 1.20 \times CP = 240 \]
\[ CP = \frac{240}{1.20} \]
\[ CP = 200 \]
Therefore, the cost price of the tube light is Rs 200.
