Percentages • Topic 8 of 8

Tips and Commissions

A tip is a percentage of a bill added for service; a commission is a percentage of sales paid to a seller. Both are straightforward "percent of an amount" calculations: tip = tip% × bill, commission = rate% × sales. A quick mental method for a 15% tip is 10% (move the decimal) plus half of that again. To find total spent including tip, multiply the bill by (1 + tip%). For commission problems you may need to find the rate (commission ÷ sales × 100) or the sales needed to earn a target commission. These are common real-world SAT contexts.

✅ Solved examples

1. What is an 18% tip on a $50 bill?
0.18 × 50 = $9.
2. A salesperson earns 5% commission on $4,000 of sales. How much is that?
0.05 × 4000 = $200.
3. A $40 bill with a 20% tip costs how much in total?
40 × 1.20 = $48.
4. A commission of $150 came from $3,000 of sales. What is the rate?
150 ÷ 3000 = 0.05 = 5%.

✏️ Practice — try these, take hints as needed

1. What is a 15% tip on a $80 bill?
0.15 × 80.
Or 10% (8) plus half (4).
Add.
$12.
2. A seller earns 8% commission on $5,000 of sales. How much?
0.08 × 5000.
Compute.
—
$400.
3. A $60 bill with a 20% tip costs how much in total?
Multiply by 1.20.
60 × 1.2.
Compute.
$72.
4. A commission of $240 came from $4,000 of sales. What is the rate?
Divide commission by sales.
240 ÷ 4000.
× 100.
6%.
5. How much sales are needed to earn $300 at a 10% commission rate?
Sales = commission ÷ rate.
300 ÷ 0.10.
Compute.
$3,000.

📝 Topic test — 8 questions

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