Due to fall in manpower, the production in a company decreases by 35%. By what percentage should the working hours be increased to restore the original production?

53.85%

According to the question,

Let's assume there are 100 men.

Man power decreased by 35%;

⇒ Man Power     Before  :  After

                          100    :   65

                           20     :   13

⇒ To restore the original production, working hours should be inversely proportional to Man power.

⇒ Man Power α \(\frac{1}{Working hours}\)

Therefore, Working hours      Before :  After

                                             13    :   20

⇒ Percentage increase = \(\frac{7}{13}\) x 100 = 53.84%