Sales Tax and Tips

For Elementary Students

What is Sales Tax?

Sales tax is extra money you pay to the government when you buy things.

Think about it like this: The price tag says $10, but at the register you pay a little more (like $10.50) because of tax!

How Sales Tax Works

Example: You buy a toy for $20. The sales tax is 5%.

Step 1: Find 5% of $20

• 5% = 5 out of 100 = 0.05
• $20 × 0.05 = $1

Step 2: Add the tax to the original price $20 + $1 = $21

Total cost: $21

What is a Tip?

A tip (or gratuity) is extra money you give to someone for good service, like at a restaurant.

Common tip amounts:

• 10% — okay service
• 15% — good service
• 20% — great service

Calculating a Simple Tip

Example: Your meal costs $30. You want to leave a 20% tip.

Step 1: Find 20% of $30

• 20% = 20 out of 100 = 0.20
• $30 × 0.20 = $6

Step 2: Add the tip to the bill $30 + $6 = $36

Total to pay: $36

Easy Trick: 10% First

Finding 10% is easy — just move the decimal point one place left!

Example: 10% of $40

• $40 → move decimal left → $4.00 = $4

Then you can use 10% to find other percentages!

20% = 10% × 2

• 10% of $40 = $4
• 20% = $4 × 2 = $8

5% = 10% ÷ 2

• 10% of $40 = $4
• 5% = $4 ÷ 2 = $2

For Junior High Students

Calculating Sales Tax (Formula Method)

Formula: Total = Price + (Price × Tax Rate)

Or: Total = Price × (1 + Tax Rate)

Example: $50 item with 7% tax

Method 1:

• Tax = $50 × 0.07 = $3.50
• Total = $50 + $3.50 = $53.50

Method 2:

• Total = $50 × 1.07 = $53.50

Both give the same answer!

Different Tax Rates

Tax rates vary by location:

• Some states: 0% (no sales tax!)
• Some states: 10% or more
• Different rates for different items (food, clothing, etc.)

Example: $25 item

• At 5% tax: $25 × 1.05 = $26.25
• At 8% tax: $25 × 1.08 = $27.00

Estimating Tax Quickly

Round the tax rate to make mental math easier.

Example: $38 item with 7% tax

Estimate:

• Round $38 to $40
• 10% of $40 = $4
• 7% ≈ a bit less than 10%, so about $2.80
• Total ≈ $40 + $2.80 = about $42.80

(Exact: $38 × 1.07 = $40.66)

Calculating Tips (Percentage Method)

10% tip: Move decimal one place left

Example: Bill is $45.00

• 10% = $4.50

15% tip: Find 10%, then add half of that

Example: Bill is $60

• 10% = $6.00
• 5% (half of 10%) = $3.00
• 15% = $6.00 + $3.00 = $9.00

20% tip: Find 10%, then double it

Example: Bill is $35

• 10% = $3.50
• 20% = $3.50 × 2 = $7.00

Tip Chart (Quick Reference)

Working Backwards (Finding Original Price)

Example: After tax, you paid $53.50. Tax was 7%. What was the original price?

Think: $53.50 = Original × 1.07

Solve: Original = $53.50 ÷ 1.07 = $50

Example: You left a $12 tip (20%). What was the bill?

Think: $12 = Bill × 0.20

Solve: Bill = $12 ÷ 0.20 = $60

Splitting Bills with Tax and Tip

Example: 4 friends share a $80 bill. Tax is 8%, tip is 20%. How much does each person pay?

Step 1: Calculate total

• Tax: $80 × 0.08 = $6.40
• Tip: $80 × 0.20 = $16.00
• Total: $80 + $6.40 + $16.00 = $102.40

Step 2: Divide by 4 $102.40 ÷ 4 = $25.60 per person

Tax on Top of Tax?

No! Tip is calculated on the before-tax amount (the subtotal), not after adding tax.

Example: Bill is $50, tax is $4, tip is 20%

Wrong: 20% of ($50 + $4) = 20% of $54 = $10.80

Right: 20% of $50 = $10.00

(Some people tip on the after-tax amount, but standard is before-tax.)

Real-World Tips

Restaurant: 15-20% is standard for good service

Delivery: $3-5 or 15-20% of order

Taxi/Uber: 15-20%

Hair salon: 15-20%

Coffee shop: $1-2 or round up

No tip needed: Fast food, retail stores

Practice