P sold a mobile phone to Q at 25% profit. However, Q sold it to R at a loss of 10%. If R paid ₹3240 for the mobile phone, what was the price (in ₹) paid by P for it?

Let's assume the cost price of mobile for P is 40y.

P sold a mobile phone to Q at 25% profit.

selling price of mobile for P = cost price of mobile for Q = 40y of (100+25)%

= 40y of 125%

= 50y

However, Q sold it to R at a loss of 10%.

selling price of mobile for Q = cost price of mobile for R = 50y of (100-10)%

= 50y of 90%

= 45y

If R paid ₹3240 for the mobile phone.

45y = 3240

y = 72

Price paid by P for mobile = 40y

= $$40\times72$$

= 2880