A merchant purchases a wrist watch for ₹ 450 and fixes

A merchant purchases a wrist watch for ₹ 450 and fixes its list price in such a way that after allowing a discount of 10%, he earns a profit of 20%. Then, the list price of the watch is

CP of watch = ₹ 450
SP of watch = 450 x [(100 + 20)/100] = ₹ 540
∴ List price of watch = (540 x 100) / (100 - 10) = ₹ 600