A vendor bought toffees at 6 for a rupee. How many for a rupee must he sell to gain 20%?

A. 3
B. 4
C. 5
D. 6
Explanation:
C.P. of 6 toffees = Re. 1
S.P. of 6 toffees = 120% of Re. 1 = Rs. 6/5
For Rs. 6/5, toffees sold = 6. For re. 1.
Toffees sold = 6 * 5/6 = 5