Field Notesgrade 7 math
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Solution key: Paychecks, budgets, and interest

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Camp · Paychecks, budgets, and interest

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1 of 8 · money-c01

Income tax is 12% of $400 in wages. Tax amount?

  1. We need the income tax ALONE, not a total with it added. Use $400 as the base.
  2. 12% = 12/100 = 0.12.
  1. Find that part: 400 × 0.12 = 48.
  2. The income tax is $48.00. Don't add the $400 wages; the question asks only for the tax.

Answer: 48 dollars

2 of 8 · money-c02

$500 in wages, 10% income tax. Take-home pay?

  1. Take-home is wages AFTER tax is removed. Start with $500 wages.
  2. 10% = 0.10. Income tax: 500 × 0.10 = $50.
  1. Subtract: 500 − 50 = $450.
  2. Take-home is $450. Check: $450 kept + $50 tax = $500.

Answer: 450 dollars

3 of 8 · money-c03

Rent is $600 of $2,000 income. What percent of income is rent?

  1. Rent is the part, $600; income is the whole, $2,000.
  2. Divide part by whole: 600 ÷ 2000 = 0.30.
  1. Convert decimal to percent: 0.30 × 100 = 30%.
  2. Rent uses 30% of income. Check: 2000 × 0.30 = $600.

Answer: 30 %

4 of 8 · money-c04

Assets $1,200, liabilities $400. Net worth?

  1. Assets are what you own; liabilities are what you owe.
  2. Net worth means assets MINUS liabilities, not their sum.
  1. 1200 − 400 = 800.
  2. Net worth is $800. Check: $800 net worth + $400 owed = $1,200 owned.

Answer: 800 dollars

5 of 8 · money-c05

Simple interest uses I = p × r × t. The principal p (starting amount) is $200, the yearly rate r is 0.05, and the time t is 3 years. How much interest, I, is earned?

  1. Simple interest uses the starting $200 every year. We want the INTEREST only, not the balance (the starting money plus the interest).
  2. 5% = 0.05. One year’s interest: 200 × 0.05 = $10.
  1. For 3 years: 10 × 3 = $30.
  2. The interest is $30.00. Adding the starting money would give the balance, a different quantity.

Answer: 30 dollars

6 of 8 · money-c06

8.25% sales tax on a $40 item. Tax amount?

  1. We need the sales tax ALONE, not a total with it added. Use $40 as the base.
  2. 8.25% = 8.25/100 = 0.0825.
  1. Find that part: 40 × 0.0825 = 3.3.
  2. The sales tax is $3.30. Don't add the $40 price; the question asks only for the tax.

Answer: 3.30 dollars

7 of 8 · money-c07

You earn $12 an hour. A bill is $48. How many hours to pay the bill?

  1. We want hours, not dollars. Each hour earns $12 toward a $48 bill.
  2. Divide dollars needed by dollars earned per hour.
  1. 48 ÷ 12 = 4 hours.
  2. Check: 4 × $12 = $48, if all that pay goes to this bill.

Answer: 4 hours

8 of 8 · money-c08

You put $100 in an account earning 5% simple interest per year. How much money is in the account after 1 year?

  1. Amount includes starting money AND interest earned.
  2. 5% = 0.05. One year’s interest: 100 × 0.05 = $5.
  1. Add to starting money: 100 + 5 = $105.
  2. The amount is $105. For just one year, simple interest and interest compounded once a year give the same answer.

Answer: 105 dollars