A shop's yearly sales rose from ₹48000 to ₹60000, while its profit rose from 15% of sales to 18% of sales. By what percent did its profit increase?

Old profit = 15% of 48000 = ₹7200; new profit = 18% of 60000 = ₹10800. The rise is ₹3600 on ₹7200 = 50%. (Sales by themselves rose 25% and the margin by 3 percentage points; neither figure answers the question, because both changes act together.)