Answer:
Statement of the given problem,
A shopkeeper made 20% profit on selling a bicycle at the labelled price but he would gain only Rs. 180 when 5% discount was allowed. What was the cost price of the bicycle?
Let C & M denote the required cost price & marked price respectively of the given bicycle.
Hence from above data we get following relations,
M = (1 + 20/100)*C
or M = (6/5)*C
(1 - 5/100)*M = 180 + C
or (19/20)*M = 180 + C
or (19/20)*(6/5)*C = 180 + C
or (57/50)*C - C = 180
or (7/50)*C = 180
or C = (50/7)*180 = 1285.71