Correct Answer - Option 3 : 80

**Given:**

The selling price of an article = Rs. 144

Profit% = Cost price

**Formula used:**

Profit% = [(SP - CP)/CP] × 100

**Calculation:**

Let the cost price of article be Rs. x.

According to the question,

Now, profit is equal to the cost price

Profit percent = x

Profit% = [(SP - CP)/CP] × 100

x = [(144 - x)/x] × 100

⇒ x^{2} = 14400 - 100x

⇒ x2 + 100x - 14400 = 0

⇒ x2 + 180x - 80x - 14400 = 0

⇒ x(x + 180) - 80(x + 180) = 0

⇒ (x - 80)(x + 180) = 0

If (x - 80) = 0, then x = 80

If (x + 180) = 0, then x = -180 (Not possible)

**∴ The cost price of an article is Rs. 80.**