A saves 35% of his income. If his income increase by 20.1% and his expenditure increase by 20%, then by what percentage do his saving increase or decrease? (correct to one decimal place)

\[\begin{array}{l} 35\% = \frac{{35}}{{100}}\\ {\rm{Income}} = 100\\ {\rm{Saving}} = 35\\ {\rm{Expenditure}} = 65\\ \begin{array}{*{20}{c}} {{\rm{Income}}}& = &{{\rm{Expenditure}}}& + &{{\rm{Saving}}}\\ {100}& = &{65}& + &{35}\\ {\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, \downarrow + 20.1}&{}&{\,\,\,\,\,\,\,\,\,\,\,\,\, \downarrow + 20}&{}&{}\\ {120.1}& = &{78}& + &x \end{array}\\ x = 120.1 - 78 = 42.1\\ {\rm{Increase \,in \,saving}} = 42.1 - 35 = 7.1\\ {\rm{Increase }}\% = \frac{{7.1}}{{35}} \times 100 = 20.3\% \end{array}\]