Percentage increase and decrease
Conservation reports, prices and populations all move in percentages. Getting the direction and the base right is most of the skill.
Part of your national curriculum
- Ratio, proportion and rates of change: Solve problems involving percentage change, including percentage increase and decrease and original value problems
Lesson overview
What you'll learn in this lesson
Calculate percentage increase and decrease
Key learning points
- • Multipliers
- • Percentage change
This lesson at a glance
- 25 minutes
- 13 parts to scroll through
- 3 quick checks
- Marked quiz at the end
- Gentle pace: short sittings with pauses
Words to know
Scroll down — the lesson carries on below
Watch & discover
Part 1 of 13
Visual introductionPicture this
Percentage increase and decrease
Conservation reports, prices and populations all move in percentages. Getting the direction and the base right is most of the skill.
In a nutshell
Calculate percentage increase and decrease
Explore the idea
Part 2 of 13
Learn
Multipliers
An increase of 15% is × 1.15. A decrease of 15% is × 0.85. Multipliers chain neatly: two 10% rises make × 1.21, not × 1.20.
Explore the idea
Part 3 of 13
Learn
Percentage change
Change ÷ original × 100. The original amount is always the denominator — using the new figure is the most common mistake in the topic.
Reset break
Part 4 of 13
Pause
That's sitting 1 of 3 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Quick check
Part 5 of 13
Quick check
Part 6 of 13
Quick check
Part 7 of 13
Reset break
Part 8 of 13
Pause
That's sitting 2 of 3 done
Stretch, get a drink, look out of the window. There is no timer and nothing is counting down — your place is saved, so you can come back in five minutes or tomorrow.
Challenge round
Part 9 of 13
Game · Sort it
Which of these are true?
Drag each card into the right column. Tap a card first if dragging is fiddly.
True
Not true
Challenge round
Part 10 of 13
Game · Fill the gaps
Finish the sentences
Choose the word that belongs in each gap.
An ____ of 15% is × 1.15.
A ____ of 15% is × 0.85.
____ chain neatly: two 10% rises make × 1.21, not × 1.20.
Challenge round
Part 11 of 13
Game · Recall cards
Increase 240 by 15%.
Card 1 of 4
Mastery quiz
Part 12 of 13
Marked quiz
End of lesson quiz: Percentage increase and decrease
4 questions, marked with the reasoning shown. No timer.
1. Increase 240 by 15%.
2. A count drops from 200 to 150. The percentage decrease is…
3. Which multiplier applies a 7% decrease?
4. 620 gorillas rise to 1,020. The increase is about…
Lesson round-up
Part 13 of 13
Lesson round-up
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Ask LunaPart 1 of 13 · Watch & discover
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Solve problems involving percentage change, including percentage increase and decrease and original value problems