Teacher Guide: Percent Concepts

@ Learning Objective 5-10 min lesson

Students will: Understand percent as "per 100," convert fluently between fractions, decimals, and percents, and calculate the percent of a number in real-world contexts.

Why this matters for FAST: Percent problems appear frequently on FAST, often in real-world contexts like discounts, tips, and taxes. Students must convert between forms and apply percent calculations accurately.

% Materials Needed

Whiteboard/projector
Student Concept Worksheet
100-grid paper
Calculator (optional)
Benchmark percent chart
Real-world examples (ads, receipts)

! Common Misconceptions to Address

Misconception #1: Moving Decimal Point Wrong Direction

Students convert 0.45 to percent as 0.45% instead of 45%, or convert 25% to decimal as 2.5 instead of 0.25.

How to Address:

"To convert decimal to percent, move decimal RIGHT 2 places (multiply by 100). To convert percent to decimal, move decimal LEFT 2 places (divide by 100). Think: percent is bigger looking, so decimal to percent gets bigger!"

Misconception #2: Confusing "Percent OF" with "Percent IS"

Students don't know whether to multiply or divide when finding percent of a number.

How to Address:

"Finding 25% OF 80 means multiply: 0.25 x 80 = 20. 'Of' means multiply! Think of it as taking a PART of the whole number."

Misconception #3: Not Recognizing Equivalent Forms

Students don't see that 1/4 = 0.25 = 25% are all the same value.

How to Address:

"Fractions, decimals, and percents are different ways to write the SAME number! 1/4 of a pizza, 0.25 of a pizza, and 25% of a pizza are all the same amount."

$ Lesson Steps

1

Introduce Percent (1 min)

SAY THIS:

"Percent means 'per 100' or 'out of 100.' The symbol % literally came from writing 'per 100' quickly! So 25% means 25 out of every 100."

2

Benchmark Percents (2 min)

Memorize These Benchmarks!

50% = 1/2 = 0.5 | 25% = 1/4 = 0.25 | 10% = 1/10 = 0.1

75% = 3/4 = 0.75 | 20% = 1/5 = 0.2 | 100% = 1 = 1.0

3

Converting Between Forms (3 min)

Conversion Rules:

Percent to Decimal: Divide by 100 (move decimal LEFT 2)

45% = 45 / 100 = 0.45

Decimal to Percent: Multiply by 100 (move decimal RIGHT 2)

0.72 = 0.72 x 100 = 72%

Fraction to Percent: Divide, then convert decimal to percent

3/4 = 3 / 4 = 0.75 = 75%

4

Finding Percent of a Number (2 min)

Find 30% of 80

Method 1: Convert to decimal and multiply

30% = 0.30, then 0.30 x 80 = 24

Method 2: Use benchmark (30% = 3 x 10%)

10% of 80 = 8, so 30% = 3 x 8 = 24

SAY THIS:

"'Of' means multiply! To find a percent OF a number, convert the percent to a decimal and multiply. Or use benchmark percents to make it easier!"

5

Guided Practice (2-3 min)

Work through these together:

Convert 0.65 to a percent (65%)
Convert 3/5 to a percent (60%)
Find 20% of 150 (30)
A shirt costs $40. It's on sale for 25% off. What's the discount? ($10)

? Check for Understanding

Quick Exit Ticket (Ask the whole class):

"What is 15% of 60?"

A) 4 B) 9 C) 15 D) 45

Correct answer: B) 9 (15% = 0.15, then 0.15 x 60 = 9, OR 10% of 60 = 6, 5% of 60 = 3, so 15% = 6 + 3 = 9)

& IXL Skills to Assign After This Lesson

Recommended IXL Practice:

Convert between percents, fractions, and decimals Find the percent of a number Percent of a number: word problems Compare percents to fractions and decimals Solve percent problems

^ Differentiation & Extension

For struggling students: Use 100-grids to visualize percent. Focus on benchmark percents (10%, 25%, 50%) before other values. Color in squares to show percents visually.

For advanced students: Challenge with percent increase/decrease problems or finding the original price after a discount.

For home: Send Parent Activity sheet. Families can calculate tips at restaurants or discounts while shopping.