A dealer allows his customer a discount of 25% and still gains 25%. If cost price of a radio is Rs. 1440, its marked price is:

Answer: Option C

Let MP = X
CP = 1440
SP = 1440 + 25% of 1440 = Rs. 1800
SP = MP - 25% of MP
SP = X - 25% of 100
SP = X - 0.25X
1800 = 0.75X
X = 2400
MP = Rs. 2400

Short-Cut
Let the marked price = Rs. x
Hence,
$$\frac{\text{75}\times \text{x}}{100}=1440\times \frac{125}{100}$$
⇒ $$\frac{1440\times 125}{75}$$  = Rs. 2400