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More Percentages

More Percentages. LSP 120 Joanna Deszcz Week 7. Successive Percentages. Overall percentage change between Final Value and Beginning Value when you are given two or more intermediate percentage decreases percentage increases or a mixture. Example.

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More Percentages

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  1. More Percentages LSP 120 Joanna Deszcz Week 7

  2. Successive Percentages • Overall percentage change between • Final Value and • Beginning Value • when you are given two or more intermediate • percentage decreases • percentage increases • or a mixture

  3. Example • Example: Jeans are on sale for 40% off the retail price. The retail price is $50.00. If you have a coupon, you can receive an additional 20% off the sale price. What is the overall percentage savings?

  4. Visually…

  5. The Math… • Determine the sale price: • 50 – (50 *.40) = 30 or 50*(1-.4) =30 • Determine the final price with coupon: • 30 – (30 *.20) = 24.00 or 30*(1-.2)=24.00 • Determine the overall percentage change: • (24.00-50)/50 • which is an overall savings of 52%.

  6. Try this one… • A politician promises, • “If elected, I will cut your taxes by 20% for each of the first three years of my term, for a total of 60%.” • Evaluate the promise.

  7. One More… • Spot prices for crude oil are rather volatile.  • From 1998 to 1999, spot prices for crude oil decreased by 28%.  • From 1999 to 2000, they increased by 106%.  • What was the percentage change over the two year period from 1998 to 2000?

  8. Reworking Percentage Change (Option 1) • Original Formula • (New-Old)/Old = % • Reworked Formulas • Old + % * Old = New or Old*(1+%)=New • Old = New 1 + %

  9. Reverse Percentage Change Formulas(Option 2) • Used when the new value and percentage are known – like a price value • Need to find the old (Original price) value • Use N= P * (1 + r) or  N= P * (1 - r) but the original value (P) is unknown.

  10. Example • Shoes at the local department store are discounted 30%. You buy a new pair of shoes and the sale price is $55.30. What was the original price of the shoes? • 55.30 = P * (1 - .30) • 55.30 = .70P • 55.30/.70 = P • 79 = P Original Price of shoes is $79

  11. More Examples… • Percentage Worksheet • This worksheet can be submitted for Extra Credit • Worth 1 homework assignment

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