Question

Rashi saves Rs 900 per month from Rs 7200. Find the ratio of her
$\begin{align}
  & \text{a) Income to saving} \\
 & \text{b) Expenditure to income} \\
 & \text{c) Savings to expenditure} \\
\end{align}$

Answer 1

Hint: Now we know that total salary is Rs 7200. Hence the income is 7200. Expenditure means the amount of money used and savings means the amount of money saved. Now we know that her savings is 900 Rs. Hence we can find the expenditure with the formula total income = expenditure + savings. Once we have all three values we can find the ratio of Income to savings, ratio of expenditure to income and the ratio of savings to expenditure.

Complete step by step answer:
Now we know that Rashi earns Rs 7200 per month.
Hence total income of Rashi is 7200
Let us call the total income as I
Hence we have $I=7200.............(1)$
Now we know that Rashi saves Rs 900 per month
Hence her total savings is 900 Rs
Now let us call this savings as S
Hence we have $S=900............(2)$
Now income is either saved or used hence we can say that the sum of total expenditure and savings is equal to total income.
Now we have total income = savings + expenditure
From equation (1) and equation (2) we get
7200 = 900 + expenditure
Rearranging the terms we get Expenditure = 7200 – 900
Expenditure = 6300
Hence the total expenditure is 6300
Let us say call this expenditure as E
Hence we have $E=6300.....................(3)$
Now let us find out the required ratios with the help of equation (1), equation (2) and equation (3).
Now the ratio of income to savings is
$\dfrac{I}{S}=\dfrac{7200}{900}=\dfrac{72}{9}=\dfrac{8}{1}$
Hence the ratio of income to savings is 8 : 1
Now the ratio of expenditure to income is
$\dfrac{E}{I}=\dfrac{6300}{7200}=\dfrac{63}{72}=\dfrac{7}{8}$
Hence the ratio of expenditure to income is 7 : 8
Now the ratio of savings to expenditure is
$\dfrac{S}{E}=\dfrac{900}{6300}=\dfrac{9}{63}=\dfrac{1}{7}$
Hence the ratio of savings to expenditure is 1 : 7.
Hence we get
$\begin{align}
  & \text{a) Income to saving = 8 : 1} \\
 & \text{b) Expenditure to income = 7 : 8} \\
 & \text{c) Savings to expenditure = 1 : 7} \\
\end{align}$

Note:
Now when we are asked to find the ratio of income to savings note that it is given by $\dfrac{income}{savings}$ and written as income : savings. Do not write it in reverse way such as $\dfrac{savings}{income}$.For example if $\dfrac{a}{b}=\dfrac{4}{3}$ then we have ratio of a is to b is 4 : 3 and ratio of b : a is 3 : 4.