Question

Stickers are bought at 11 for Rs. 10 and sold at 10 for Rs. 11. Find the profit per cent.

Answer 1

c.p of 11 stic..=10
c.p of 1 stic..=10/11
s.p. of 10 stic...= 11
s.p of 1 stic..= 11/10
s.p > c.p 
hence, 
profit= s.p. - c.p.
        =11/10 - 10/11
         = 21/110
p %= p/c.p. * 100
      = {(21/100)/10/11}*100
      =231/10 %
      = 23.1%
answer, hope it will help