Correct Answer - Option 2 : 72.55%

**Given:**

Allowing successive discounts of 25% and 15% on the pen gives a net gain of 10% on cost.

**Concepts used:**

M.P. = S.P. + Discount

Discount % = Discount/M.P. × 100

Gain % = Gain/C.P. × 100

Gain = S.P. – C.P.

**Calculation:**

Allowing successive discounts of 25% and 15% on the pen gives a net gain of 10% on cost. Let M.P. of article be Rs. x.

⇒ Total discounts = (x/4) + {15% × (x – (x/4))} = 29x/80

⇒ S.P. = M.P. – Total discounts

⇒ S.P. = x – (29x/80) = 51x/80

A net gain of 10% is made on cost.

Gain % = Gain/C.P. × 100

Let C.P. be Rs. y.

⇒ 10 = (51x/80 – y)/y × 100

⇒ 11y/10 = 51x/80

⇒ y = 51x/88

Percentage by which M.P. must be marked over C.P. = {(x – 51x/88)/(51x/88)} × 100 = 72.55%

**∴**** M.P. must be marked over C.P. by 72.55%. **