The wholesale price per unit of an item is Co up to first 19 units. The unit price falls by 10% if 20 to 29 units are purchased, and by another 10% if 30 or more units are purchased. If 120 units are bought, the unit price paid is

Correct option is D

Solution:

Base unit price = C₀

For:

Up to 19 units → price = C₀

20–29 units → 10% discount → 0.90 C₀

30 or more units → additional 10% discount on 0.90 C₀
=> Total discount = 10% of 0.90 C₀ = 0.09 C₀
=> New price = 0.90 C₀ − 0.09 C₀ = 0.81 C₀

If 120 units are bought, the unit price = ?
Since 120 ≥ 30, apply both discounts.
Final unit price = 0.81 C₀

Final Answer:
S. Ans. (D) 0.81 C₀