Practice Set · Part 1
Find and Compare with Percentages
Pick up where we left off
Where we left off
Our goal: I can find the percent of a number using an equation or a model, explain what each part stands for, and build one for a situation I have not seen before.
The big idea: A percent of a number depends on both the percent and the base, so find each part before you compare.
Model to copy — Example · Compare two discounts
- Prize A costs 80 tickets and is 25% off. Prize B costs 60 tickets and is 30% off. Which prize saves you more tickets?
- Write 100% and both prices in the first column: 100% : 80 : 60
- Divide by 4 to find 25% for Prize A: 80 ÷ 4 = 20
- Find 5%, then multiply by 6 for Prize B: 60 ÷ 20 = 3; 3 × 6 = 18
- Compare the two discounts: 20 > 18
- Prize A saves more: 20 tickets, compared with 18 tickets for Prize B.
Start here
You did these with your group. Now do them on your own — the model above is yours to copy.
- 1
Same stepsFinish what the group started. Use the model above, step for step.
Try it together — then prove it: Find 40% of 80. What number matches 100% in the first column? (80) Divide both by 5. What is 20% of 80? (16) What do you multiply 20% by to reach 40%? (× 2) Do the same to the other row. What is 40% of 80? (32) Why must 40% of 80 be less than 80? (100% matches 80. 40% is less than 100%, so its part is less than 80.)Show your work - 2
Warm restartWhich benchmark percent is closest to 9%?
- A1%
- B10%
- C25%
- D50%
How do you know?
- 3
Warm restartEstimate 24% of 80 using a benchmark percent.
- Aabout 8
- Babout 20
- Cabout 24
- Dabout 40
How do you know?
- 4
Warm restartA jacket costs $39.75. Estimate a 20% discount.
- Aabout $2
- Babout $4
- Cabout $8
- Dabout $20
How do you know?
Practice Set · Part 2
Find and Compare with Percentages
Keep going
You answered these out loud. Now write them.
Answer, then say how you know — the reason is the part that counts.
- 5
Think it throughWhat is 12% written as a decimal?
- A0.012
- B0.12
- C1.2
- D12
Why is that the answer?
- 6
Think it throughWhat is 12% of 1,500 tickets?
- A1.8
- B18
- C180
- D1,800
How do you know? Give a second reason as well.
- 7
Think it throughCheck with a benchmark: what is 10% of 1,500?
- A1.5
- B15
- C100
- D150
Explain your thinking. What would have to change for a different choice to be right?
- 8
Back to the modelWhat steps do you follow every time you find the percent of a number?
Practice Set · Part 3
Find and Compare with Percentages
Words and reasoning
Word bank · Banco de palabras
Use the words
Fill each blank with a word from the bank.
- A number out of 100 is a ___.
- The whole amount you start with, right after the word “of,” is the ___.
- The amount you get out of the whole is the ___.
- A number sentence with an equal sign, like part = percent × base, is an ___.
Explain the thinking
- 9
Find the mistakeAnother student made this exact mistake in this lesson. Explain why it is wrong, then write what they should have done.
The mistake: A common mistake in Find the Percent of a Number is multiplying by the percent number itself instead of its decimal form — for example, finding 30% of 80 by computing 30 × 80 = 2,400 instead of 0. - 10
Say moreWhat steps did you follow every time to find the percent of a number in the discount table?
- 11
Write your ownWrite your own problem about this situation, then solve it and show the answer. The situation: Five phone battery icons are lined up in order. The first is full at 5 bars out of 5, and each one after it has one fewer bar. The last icon has 1 bar left, and the caption says about 1 hour remains.
Show your work
Practice Set · Part 4
Find and Compare with Percentages
Show what you know
Last check
These two come from Lesson 4.3. If they are shaky, that is the lesson to revisit — not this one.
- 12
Show what you knowExplain your thinking — What is 45% of 360?
- A45
- B162
- C180
- D315
Explain your choice.
- 13
From Lesson 4.3Explain your thinking — Estimate 19% of 412 using benchmarks or compatible numbers.
- AAbout 8
- BAbout 40
- CAbout 80
- DAbout 200
How do you know?
- 14
From Lesson 4.3Photos take up 3.5 of the 4 GB of used storage. About what percent of the used storage is photos?
- AAbout 35%
- BAbout 58%
- CAbout 87%
- DAbout 99%
How do you know?
Be honest — this tells your teacher what to do next
| I can… | Not yet | Getting there | Got it |
|---|---|---|---|
| I can find the percent of a number using an equation or a model, explain what each part stands for, and build one for a situation I have not seen before. | |||
| I can explain why it works: A percent of a number depends on both the percent and the base, so find each part before you compare. | |||
| I can justify my answer to a skeptic and connect it to a second strategy or representation. |
One question I want to ask my group next time