A person allows a 10% discount for cash payment from the marked price of a toy and still he makes a 10% gain. What is the cost price of the toy which is marked Rs. 770 ?

(a) Rs. 610
(b) Rs. 620
(c) Rs. 630 ✓ UPSC's answer
(d) Rs. 640

Why the answer is (c)

• The marked price of the toy is given as Rs. 770.

• A 10% discount is allowed on the marked price, so the discount amount is 10% of 770, which is Rs. 77.

• The selling price (SP) is the marked price minus the discount: 770 - 77 = Rs. 693.

• The seller makes a 10% gain on the cost price (CP), meaning SP = 110% of CP.

• Therefore, CP = SP / 1.10 = 693 / 1.10 = Rs. 630.

• Thus, the cost price of the toy is Rs. 630, which corresponds to option (c).

Why the other options are wrong

(a) Rs. 610: Rs. 610 is incorrect because it does not satisfy the condition that a 10% gain on this cost price would result in a selling price of Rs. 693.
(b) Rs. 620: Rs. 620 is incorrect because 110% of 620 is Rs. 682, which is not equal to the calculated selling price of Rs. 693.
(d) Rs. 640: Rs. 640 is incorrect because 110% of 640 is Rs. 704, which is not equal to the calculated selling price of Rs. 693.

Asked in the CSAT Paper II of the UPSC Civil Services Preliminary Examination 2016, held on 7 August 2016. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.