Lesson 4 - Reverse percentage problems

Objective

To use multipliers to find the original amounts after percentage changes have taken place

Resources

Rulers, calculators, IWB, computers for extension [optional]

Starter

Play the memory game with students to remind them of the multipliers for percentages, percentage increases and percentage decreases.

Lesson

Go through the lesson presentation with the students. You may need to go through more examples with the students showing why you must divide when looking at reverse percentage problems.

Activity

Hand out the worksheet; students must complete the worksheet by working out the original values before the percentage calculations are done. Insist that if students get a line that is not horizontal or vertical then they have made a mistake. Go around the class checking that the mazes being drawn are correct! Students should work in pencil as mistakes are common.

If a student finishes, ask them to do the extension which involves finding the original amount after repeated percentage changes – remind them of what they did last lesson. Again it can either be done on computer or printed out and done as a worksheet.

Plenary

Open up the plenary activity and run the slideshow. Ask the students to match the reverse percentage problems in the middle to the rotating original values in the corners. Take a variety of student responses [hands up for 50, 60, 70 80] and click on the problem. It will bounce around the screen before eventually settling on the correct answer.

Download the lesson 4 plan in Word format

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