1. Lesson Objective By the end of the lesson you should be able to work out the multipliers for percentage increases and decreases. You should also be able to use these to calculate new values after the changes have taken place.

2. Percentage increase and decrease To work out a percentage increase or decrease we can follow these steps. 1.Work out the percentage like we did last time. 2.Add it on for an increase or take it away for a decrease. example 1– increase £120 by 15% 15% of 120 = 0.15 x 120 = 18 120+18= £138

3. Percentage increase and decrease This method is fine but can cause problems later on. Using multipliers can make this much quicker. Let’s look at example 1 again example 1– increase £120 by 15% We can think of the £120 as the original 100%. Now we want the original price and an extra 15%. That is 100% + 15% = 115% The multiplier for 115% is 1.15 So 1.15 x 120 = 135

4. Percentage increase and decrease Although this may seem more complicated, most of it can be done in your head. Here are some more examples (you can probably do the first two steps in your head) increase 130 by 12%1.12 x 130 = 145.6100%+12%=112%112% = 1.12 increase 250 by 23%1.23 x 250 = 307.5100%+23%=123%123% = 1.23 increase 64 by 3%1.03 x 64 = 65.92100%+3%=103%103% = 1.03 increase 562 by 86%1.86 x 562 = 1045.32100%+86%=186%186% = 1.86

5. Percentage increase and decrease If we add the percentage on to 100 for increases. What do you think we do for decreases? Here are some examples, again the 1 st two steps can probably be done in your head. decrease 130 by 6%0.94 x 130 = 122.2100%-6%=94%94% = 0.94 decrease 750 by 34%0.66 x 750 = 495100%-34%=66%66% = 0.66 decrease 17 by 94%0.06 x 17 = 1.02100%-94%=6%6% = 0.06 decrease 238 by 0.3%0.997 x 238 = 237.286100%-0.3%=99.7%99.7% = 0.997

6. 50% increase 75% decrease 25% increase 9% decrease 5% increase 9% increase 95% decrease 75% increase 50% decrease 5% decrease 1.75 0.95 0.05 0.5 1.5 0.25 0.91 1.05 1.09 1.25 Match up these percentage changes with their multipliers Pen (press esc to cancel)

7. Percentage increase and decrease There are two types of questions on your sheet. For the first 10 join the percentage change to its multiplier. For the rest join the question to its answer. Use straight lines only and join dot to dot, each line should pass through a letter. If you do them in order and make a note of the letters you are passing through you should get a message.