UPSC CSE Prelims 2016
The problem requires determining the Cost Price (CP) of a toy given its Marked Price (MP), the discount offered, and the percentage gain achieved.
Discount = (10/100) * 770 = Rs 77.
SP = MP - Discount = 770 - 77 = Rs 693.
SP = CP + (Gain % of CP)
SP = x + (10/100)x
SP = (11/10)x.
(11/10)x = 693
x = 693 * (10/11)
x = 63 * 10
x = 630.
Options 1 (Rs 610), 2 (Rs 620), and 4 (Rs 640) are incorrect. If any of these values were the Cost Price, the resulting Selling Price after a 10% gain would not be consistent with the Selling Price derived from a 10% discount on the Marked Price of Rs 770, as established by the correct calculation.