A person sold an article for ₹ 3600 and got a profit of 20%. Had he sold the article for ₹ 3150, how much profit would he have got?

Let the cost price of the article be ₹ N.
Now, N + 20N/100 = 3600
⇒ 120N/100 = 3600
∴ N = 3000
Now, profit percentage when the article is sold for ₹ 3150 = [(3150 - 3000)/3000] x 100
= (150/3000) x 100 = 5%