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Percentage Review Math 8

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Percentage Review Math 8

  1. 1. Math 8 <br />Unit 2 – Percentage Review<br />
  2. 2. Simple Interest<br />Mr. Otto wanted to build a garage. Therefore, he had to borrow money from the bank. He borrowed $7,000 at a rate of 5% for 30 months. <br />What is the amount of interest he had to pay on the loan?<br />
  3. 3. Answer – Simple Interest<br />I = Prt<br />I= $7,000(.05)(30/12)<br />I= $875<br />
  4. 4. Compound Interest<br />Dr. Winslow wants to open a medical office in Levering but does not have the money to do so. Therefore, he gets a loan from the bank. He borrows 120,000 at an interest rate of 8% which is compounded semi-annually for 9 years.<br />How much will he pay back altogether?<br />
  5. 5. Answer – Compound Interest<br />A= P(1 + r/n)n*y<br />A=$120,000(1 + .08/2)2*9<br />A=$120,000(1+ .04)18<br />A= $120,000(1.04)18 <br />A= $243,097.98<br />
  6. 6. Multiple Discounts<br />A $900.00 Dell Laptop was marked down 25% for a Christmas special. It did not sell on Black Friday so it was marked down another 15%. It still did not sell so it was marked down another 10% and it sold then within an hour.<br />How much did the laptop sell for?<br />
  7. 7. Answer – Multiple Discounts<br />Remember use the % it is actually worth – NOT the % discount.<br />$900 (.75)(.85)(.90) <br />$516.38<br />
  8. 8. Ratio Units<br />Raymond gets paid $550 for dropping off scrap metal to the junk yard. His scrap totals 2.75 ton. What is the price he is paid per ton of scrap metal?<br />
  9. 9. Answer – Ratio Units<br />Price per ton?<br />$550/2.75 ton<br />$200 per ton<br />
  10. 10. Simple Interest – Total Amount<br />Gracie needs to borrow $1,000 to buy the dog of her dreams. She borrows the money from Capital Bank at a rate of 6.5% for 5 years. <br />What is the total payback amount?<br />
  11. 11. Answer – Simple Interest Total Amount<br />I = Prt<br />I= $1,000(.065)(5)<br />I= $325<br />$1,000 + $325 = $1,325<br />
  12. 12. Multiple Discounts<br />A new Camaro costs $45,000 brand new. The car depreciates in value 22% each year. What will it be worth in 7 years?<br />
  13. 13. Answer – Multiple Discounts<br />Remember use the % it is ACTUALLY worth!<br />$45,000(.78)7<br />$7,904.51<br />
  14. 14. Proportions<br />30 = ______% of 75<br />
  15. 15. Answer - Proportions<br />Is/of and %/100%<br />30/75 n/100%<br />Cross multiple 30 * 100 = 3000<br />3000 / 75 = <br />40%<br />
  16. 16. % Increase<br />You buy an IPod touch for $258 with 6 % sales tax. What is the total price?<br />
  17. 17. Answer - % Increase<br />Always start with 100%<br />100% + 6% ($258)<br />106% ($258)<br />1.06($258)<br />$273.48<br />
  18. 18. Simple Interest – Find the Rate<br />What is the simple interest rate for a snowboard that costs $680 with a loan for 2 years and interest of $170?<br />
  19. 19. Answer – Simple Interest find the rate<br />Work backwards from I=Prt<br />$170 = $680(r)(2)<br />$170 / $680 / 2<br />.125 = 12.5%<br />
  20. 20. Perfect Squares<br />42 is between what two perfect squares?<br />
  21. 21. Answer – Perfect Squares<br />First find the square root of 42<br />6.48 so it is between 6 and 7<br />6’s perfect square is 6 * 6 = 36<br />7’s perfect square is 7 * 7 = 49<br />36 & 49<br />
  22. 22. Cube Root<br />The cube root of 189 is between what two integers?<br />
  23. 23. Answer – Cube Root<br />To find the cube root you need to put the number to the 1/3 power.<br />5.74<br />5 & 6<br />
  24. 24. Credits<br />All of the images in this review presentation were thanks to Google Images !!<br />

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