A shopkeeper sells an item at 10% gain. If he had bought it at 10% less and sold it for Rs. 2 less, he would have gained 16 2/3%. Find the cost price.

Explanation

CP=100x. SP=110x. New CP=90x. New gain=16.66% of 90x = 15x. New SP=105x. 110x-105x=2 => 5x=2 => x=0.4. CP=100*0.4=40? Wait, recalculate: 1.1666 * 90x = 105x. 110x-105x=2 => 5x=2 => x=0.4. CP=100x=40? Recheck: 10% gain on 120 is 132. Buy 10% less=108. 16.66% gain on 108 is 18. 108+18=126. Diff=6. If CP=120, x=1.2. Then 5x=6 => x=1.2. CP=100*1.2=120.