What is r-40?

A man sells an article at a profit of 25 percent . if he had bought it at 20 percent less and sold it for Rs.10.50 less. he would have gained 30 percent . Find the cost price of the article?

(A): s = 5c/4. (B): (s - 10.5) = 13(4c/5)/10 Substitute A in B (5c/4 -10.5) = 52c/50 ie 5c - 42 = 208c/50 5c = 4.16c + 42 0.84c = 42 c = 50 Original cost price R50, original selling price R62.50 Theoretical cost price R40, theoretical selling price R52, profit 12/40 = 30%. QED I enjoyed this one, it actually worked straight out on the keyboard!