A man spends 65% of his income. His income increases by 20% and his expenditure also increases by 10%. The percentage of increase in his savings is ________.

38.5%

Let income = 100x

expenditure = 65% of 100x = 65x

 &  saving = 100x - 65x = 35x

Increased income = 100x + 20% of 100

= 100x + \(\frac{1}{5}\) × 100x = 120x 

increased expenditure = 65x + 10% of 65

= 65x +\(\frac{1}{10}\) ×65

=  71.5x

New saving = 120x - 71.5x = 48.5x

increased percentage of saving = \(\frac{13.5x}{35x}\) × 100% = 38.5%