A person spends 40% of his monthly income. The monthly income of the person is increased by 15% and his expenditure is decreased by 22%. What is the approximate percentage increase in his savings?

40%

Let total income = 100x

Expenditure = 40% of 100x = 40x

Saving = 100x - 40x = 60x

New income = 100x + 15% of 100x = 115x

New Expenditure = 78% of 40x = 31.2x

New Saving = 115x - 31.2x = 83.8x

Required percentage = \(\frac{83.8x - 60x}{60x}\) × 100

= 39.666%

= 40%   (approx)