KS3

How to work out a percentage decrease (decimal method)

Part ofMathsPercentages

To play this video you need to enable JavaScript in your browser.

This video can not be played

A one-minute video showing how to work out a percentage decrease.

How to work out percentage decrease

Skip image gallery

Image caption,
Click to see a step-by-step slideshow.
Image caption,
WHAT YOU NEED: whiteboard, marker pen, calculator and ruler.
Image caption,
STEP 1: Draw a bar and label it with the total amount - in this case £20. Roughly estimate where 75% would be and draw a vertical line. Shade the larger area in and label this with a question mark. Draw a bar directly underneath.
Image caption,
STEP 2: Label 100% at the end of the bar and draw a vertical line directly below the vertical line above. Label the section at the end of the bar 25%. Shade the larger area and label 75% above the vertical line.
Image caption,
STEP 3: Convert each percentage to a decimal by dividing it by 100. On the bottom bar change the 100% label to 1, change the 25% label to 0.25 and change the 75% label to 0.75.
Image caption,
STEP 4: Multiply the original amount by the decimal to find the amount after the decrease. Here it's £20 multiplied by 0.75. Before using a calculator, can you estimate what the answer might be in your head?
Image caption,
Now use a calculator to check your answer. £20 reduced by 25% is £15.
Image caption,
You’ve done it! Can you visualise this in context? How much would 30% off the marked price be?

Where next?

Discover more maths topics on Bitesize.

More on Percentages

Find out more by working through a topic

How to find the original value before % off (decimal method)
count
8 of 9
How to work out interest
count
9 of 9
Percentages
count
1 of 9
Percentage Change
count
2 of 9