Q530
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)
A.
20.3% of increase
AnswerB.
18.5% of decrease
C.
19.75% of decrease
D.
21.9% of increase
Answer: Option A
Solution
Answer: Option A
Solution:
\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}