The price of oranges is ₹ 90 per dozen. Manoj can buy 12 dozen oranges with the money he has. If the price of orange is increased by ₹ 30, how many oranges can Manoj buy?

Cost of 1 dozen oranges = ₹ 90

Cost of 12 dozen oranges = ₹ 90 x 12 = ₹ 1,080

Price of oranges is increased by ₹ 30,

∴ New price of 1 dozen oranges = ₹ (90 + 30) = ₹ 120

Let Manoj buy x dozen oranges for ₹ 120 per dozen.

As the price of oranges has increased, so now Manoj will be able to buy lesser number of oranges with the money he has.

∴ It is a case of inverse variation.

$\therefore 12 \times 90 = x \times 120\\[1em] \Rightarrow 1080 = x \times 120\\[1em] \Rightarrow x = \dfrac{1080}{120}\\[1em] \Rightarrow x = 9$

Hence, Manoj can buy 9 dozen oranges for ₹ 1,080.