A person buys a certain number of oranges at ₹84 a dozen and two times of it at ₹72 a dozen. He sells all the oranges at ₹90 a dozen and makes a profit of ₹1680. How many oranges does he buy?

Let the person is buying 1 dozen of oranges at the rate of ₹84 per dozen and 2 dozen of oranges at the rate of ₹72 per dozen.

Cost of 1 dozen orange = ₹84

Cost of 2 dozen oranges = ₹72 $$\times\ 2=144$$

Total cost of 3 dozen orange = ₹84 + ₹144 = ₹228

Selling price of 1 dozen banana = ₹90

Selling price of 3 dozen banana = ₹90$$\times\ 3=270$$

profit = 270 - 228 = ₹42

Profit ₹42 for buying 3 dozen oranges.

According to question profit = ₹1680 (given)

So number of oranges = $$\ \frac{1680}{42}\times\ 3=120$$ dozens

total number of oranges = 120$$\times\ 12=1440$$

Hence, Option C is correct.