Most math involved in a household budget is adding, subtracting, multiplying, and dividing.
1.
A family has two people contributing income to the household
budget. The first person makes $550 a week and the second person makes
$600 a week. They expect to pay 9% of their income in taxes. If they
budget a 30 day month, how much money should they expect to have each
month after taxes?
We first can calculate how much the family makes before taxes per week.
\[\$550 + \$600 = \$1150\]
We can then calculate how much money they will have after taxes. If they pay 9% of their income in taxes, that means they will have 91% left over after taxes.
\[\$1150 \cdot 0.91 = \$1046.50\]
The family makes $1,046.50 after taxes per week.
If there are 30 days per month, then we can divide 30 by 7 to calculate the number of weeks per month.
\[30 \div 7 \approx 4.2857\]
There are approximately 4.2857 weeks in a month. That means the family’s take home pay after taxes per month is
\[\$1046.50 \cdot 4.2857 \approx \$4,484.99\]
2.
The family wants their rent to be 30% of their before-tax income,
their groceries to be 15% of their before-tax income, and their car
expenses to be 20% of their before-tax income. How much money should
they plan on having for each of these three items per month, and how
much money is left over after taxes?
First, we need to calculate their before-tax income. Using 4.2857 weeks per month, their before-tax income is
\[\$1150 \cdot 4.2857 \approx \$4,928.56\]
If rent is 30% of their before-tax income, their monthly rent is
\[\$4,928.56 \cdot 0.30 = \$1,478.57\]
If groceries are 15% of their before-tax income, their monthly rent is
\[\$4,928.56 \cdot 0.15 \approx \$ 739.28\]
If car expenses are 20% of their before-tax income, their monthly allowance is
\[\$4,928.56 \cdot 0.20 = \$985.71\]
To calculate the amount left over after taxes, we take their monthly income after taxes, \(\$4,484.99\), and subtract each of these items.
\[\$4,484.99 - \$1,478.57 - \$739.28 - \$985.71 = \$1,281.43\]
The family has $1,281.43 left over after taxes and these three expenses.
3. If the family above has a monthly credit card debt of $200, what percent of their before-tax monthly income goes to their credit card?
The family’s before-tax monthly income is \(\$4,928.56\). To calculate the percent of their income that is credit card debt, we divide the credit card debt by the income and multiply by 100.
\[\frac{\$200}{\$4,928.56} \cdot 100 \approx 4.06\%\]
Approximately 4% of their monthly income goes to their credit card debt.
1. A family has two people contributing income to the household budget. The first person makes $750 a week and the second person makes $400 a week. They expect to pay 12% of their income in taxes. If they budget a 30 day month, how much money should they expect to have each month after taxes?
2. The family wants their rent to be 35% of their before-tax income, their groceries to be 10% of their before-tax income, and their car expenses to be 20% of their before-tax income. How much money should they plan on having for each of these three items per month, and how much money is left over after taxes?
3. If the family above has a monthly credit card debt of $300, what percent of their before-tax monthly income goes to their credit card?
1. What do you consider to be a good percentage of a family’s income to go to rent? To groceries? To car payments?