A man sold some ₹ 20 shares, paying 8% dividend, at 10% discount and invested the proceeds in ₹ 10 shares, paying 12% dividend, at 50% premium. If the change in his annual income is ₹ 600, find the number of shares sold by the man.

By selling an article for ₹ 24, a man gains as much percent as its cost price. Find the cost price of the article.

B takes 16 days less than A to do a certain piece of work. If both working together can complete the work in 15 days, in how many days will B alone complete the work ?