The price of a share fell by 20% in one week and by a further 25% in the next. By what percent must it now rise to get back to the price it had before the two falls?

Take the old price as ₹100: it becomes $100\times 0.80\times 0.75=$ ₹60. To climb from ₹60 back to ₹100 the rise is ₹40 on a base of ₹60 = 66.67%. (Adding the two falls gives 45%, which is not even the total fall — that is 40%. And the fall of 40% is measured on ₹100 while the recovery is measured on ₹60, which is why the two percentages differ.)