Some toffees are bought at the rate of 11 for Rs 10 and the same number at the rate of 9 for Rs 10. If the whole lot is sold at one rupee per toffee, find the gain or loss percent on the whole transaction.
In set (i)
CP of 11 toffees = Rs.10
CP of 1 toffee = Rs. 
In set
CP of 9 toffees = Rs.10
CP of 1 toffee = Rs.
After mixing both sets ….
CP of 2 toffees = 
CP of 1 toffee = Rs. 
SP of 1 toffee = Rs
Loss = 
= 
20