After allowing a discount of 20% on the marked price of a lamp, a trader loses 10%. By what percentage is the marked price above the cost price?
Rate of discount =20%
Loss =10%
Let the cost price of the lamp = Rs. 100
Loss =10%
\therefore Selling price = Rs. 100 - 10 = Rs. 90
Rate of discount =20%
∴ Marked price (M.P) =S.P×100100−discount%
=90×100100−20=90×10080=Rs.2252=Rs.112.50
∴ Difference in M.P and C.P = Rs. 112.50 - Rs. 100 = Rs. 12.50
∴ Percentage of difference
=12.50×100100=12.50%=12.5%