Ramesh sold a phone at a loss of 5%. Had he sold it for Rs. 200 more, he would have gained 15%. To gain 25%, he should sell it for :

Let the cost price (C.P.) of the phone be Rs. x.

Selling price (S.P.) of the phone = x - (5% of x) = x - 0.05x = 0.95x (∵ S.P. = C.P. - Loss)

If S.P. is Rs. 200 more: -

Gain% = 15%

⇒ Gain = 15% of x = 0.15x

S.P. of the phone = 0.15x + 200

⇒ x + 0.15x = 0.95x + 200 (∵ S.P. = C.P. + Gain)

⇒ 1.15x = 0.95x+200

⇒ 0.2 x = 200

⇒ x = Rs. 1000

If gain is 25%: -

Cost price (C.P.) of the phone be Rs. 1000

⇒ S.P. of the phone = (1000 + 25% of 1000) = 1000 + 250 = Rs. 1250

∴ To gain 25%, he should sell for Rs. 1250.