Math lesson plan · 7th grade (Year 8 in England) · 30 minutes
Increase an amount by a percentage
Decimals and percentages
CCSS 7.RP.A.3England: KS3 NumberEngland: GCSE Foundation Ratio
Objective and success criteria
Students will: Increase an amount by a percentage.
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Percentage of an amount
Leads to: Find the percentage change; Markup, profit and commission; Use decimal multipliers for percentage change
Materials: Place value chart with tenths and hundredths, Hundred squares, Number lines, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 4 min
- Quick retrieval from earlier learning (Percentage of an amount). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- What is 40% of 330? → 132Prompt: Find 10% (or 1%) first, then build up.
- Find 8% of 180. → 14.4Prompt: 10% of 180 is 18. What are 5% and 1%?
- There are 440 students at an event. 40% of them arrive by bike. How many arrive by bike? → 176Prompt: Find 40% of 440.
Hook · 3 min
- Show two prices or race times with decimals and ask which is bigger, then why.
- Share the objective: Increase an amount by a percentage. Read the success criteria together.
I do: model it · 7 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: Increase 360 by 50%.
- Step 1: 50% × 360 = 180
- Step 2: 360 + 180 = 540
- Answer: 540
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 6 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- Increase 520 by 50%. → 780Prompt: Find 50% of 520.
- A video had 6100 views. Views went up by 15% the next day. How many views did it have then? → 7015Prompt: Increasing by 15% means you end up with 115%.
You do: independent practice · 7 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 6 questions are on the student sheet below, with answers in the key.
Exit ticket · 3 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- A video had 6200 views. Views went up by 4% the next day. How many views did it have then? → 6448Prompt: Increasing by 4% means you end up with 104%.
- Chloe increases 320 by 50% and then decreases the answer by 50%. Chloe expects to get back to 320. What does Chloe actually get? → 240Prompt: The second percentage is of a different (bigger) amount.
Watch out for
- Thinking 0.45 is bigger than 0.5 because 45 is bigger than 5.
- Moving the digits the wrong way when multiplying or dividing by 10.
Support and stretch
Support
- Review first: Percentage of an amount.
- Use concrete materials: place value chart with tenths and hundredths.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Move on to: Find the percentage change; Markup, profit and commission; Use decimal multipliers for percentage change.
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/math/grade-7.
Free lesson plan from eurekami.com/lesson-plan-builder