A $64 taxable subtotal has a stated 5% tax
- Tax = 64 × 0.05 = $3.20.
- Total = 64 + 3.20 = $67.20.
- Equivalent method: 64 × 1.05 = $67.20.
Taxes, tips & final totals
Add the extra amount to a clearly stated base.
An increase uses the original amount plus the added part
For a stated tax rate t% on a taxable subtotal S, tax = S × t/100 and total = S × (1 + t/100). For a tip, first identify the base requested in the problem. A tip calculated on a pre-tax subtotal differs from a tip calculated on a tax-included total.
Follow the subtotal through each step.
Predict first. Change one value, then explain what stays the same and what changes. All bars use the same scale within a model.
Combine rates only when the base is the same
In a classroom example, a 5% tax and 15% tip both calculated on the same $40 subtotal add $2 and $6, for $48. If the tip is instead 15% of $42 after tax, the tip is $6.30 and the total $48.30. State the assumption before calculating.
Use the rates supplied in the question
These lessons use hypothetical shopping rules, including an illustrative 5% tax where stated. They are mathematical models, not a statement that every item is taxable or every place has the same rate. Apply coupons and tax in the order specified by the classroom task, and round payments consistently.
Worked examples
A $50 meal: 12% tip and 5% tax on the subtotal
- Tip = 0.12 × 50 = $6. Tax = 0.05 × 50 = $2.50.
- Total = 50 + 6 + 2.50 = $58.50.
- Both percentages use $50, so 50 × 1.17 also works.
Guided Practice
An $80 item is 25% off, then has a stated 5% tax on the sale price. What is paid?
A first hint
Find the discounted subtotal first, then add the tax on that amount.
Compare your reasoning
$80 × 0.75 = $60; tax = $3; total = $63.
Practice
Fresh questions · useful feedback
Build fluency, one decision at a time.
Work through eight questions. Two independent correct answers introduce a harder version; supported answers bring the next question back to the foundation. You can use hints at any time.
0 of 8 questions completed
This round saves on this device. It is practice, not a school mark.
Connections
Under the same classroom tax rule, a tax-included total is $84 at 5%. Recover the subtotal and tax. Explain why subtracting 5% of $84 is incorrect.
Use it in Extreme Couponing
Record the whole, the percent multiplier and the result with units. For each coupon, use the eligible amount at that step. State whether a resale percentage means percent of cost or markup on cost.