DRDO Multi tasking staff Model paper 9

Given:
Selling price of 4 article in Rs. = 1
Selling price of 1 article in Rs. = 1 / 4 = 0.25
Let,
The cost price of 1 article in Rs. = x
Profit percentage =

Selling‌Price−Cost‌Price

Cost‌Price

×100%
⇒ 25 = [(0.25 - x) / x] × 100
⇒ 0.25x = 0.25 - x
⇒ 1.25x = 0.25
⇒ x = 0.20
Cost price of 1 article in Rs. = 0.20
Now,
Selling price of 6 article in Rs. = 1
Selling price of 1 article in Rs. = 1 / 6
Loss percentage =

Cost‌Price−Selling‌Price

Cost‌price

×100%
Loss percentage = [(0.20 - (1 / 6)) / 0.20] × 100
Loss percentage = (0.20 / 1.20) × 100
∴ Loss percentage = 16.67%