November 20, 2013

 Watch: describing-the-meaning-of-percent describing-the-meaning-of-percent  “Per” means “out of” or “divided by”  “Cent” means “one hundred”  So “percent” literally means “out of 100” or “divided by 100”

 To convert a decimal to a percent, move the decimal point two places to the right and add the % sign.  Example: 0.56 = 56%  1 = 100%  1.5 = 150%  4 = 400%

 To convert a percent to a decimal, remove the % sign and move the decimal point two places to the left.  Example: 25% = 0.25  100% = 1  “Sales increased 400% this year!” means that sales increased by 4 times last year’s amount, because 400% = 4.

 here.com/multiple_choi ce_polls/mpM1npuC8G rWp2O here.com/multiple_choi ce_polls/mpM1npuC8G rWp2O  Correct answer: 8/10,000  Eight hundredths of a percent means 0.08 divided by 100, which is or eight ten- thousandths

 What is 5% of 100?  % means out of 100, so 5% of 100 is 5.  What is 5% of 200?  5 out of each 100  5 ∙ 2 = 10  What is 5% of 300?  5 ∙ 3 = 15  You can use this method with any multiple of 100.

 Percent ∙ Base = Amount  Base is the quantity we are drawing from  Base quantity usually comes after the word “of” or “out of”  Example: “What is 25% of 800?”  Percent = 25%  Base = 800  Amount = unknown = x

 Percent ∙ Base = Amount  25% ∙ 800 = x  Need to convert the percent to a decimal  0.25 ∙ 800 = 200  So 25% of 800 is 200.  Does that make sense?  25% is one-fourth.  200 is one-fourth of 800.

 Percent ∙ Base = Amount  Percent is unknown  Base is 32  Amount is 20  x ∙ 32 = 20  Divide each side by 32  x = 20 ÷ 32  x =  Need to convert to a percent  20 is 62.5% of 32.

 9)40% of 30 is 12.  10)60% of 500 is 300.  11)8 is 25% of 32.  12)24 is 12% of 200.  13)58.5% of 50 grams is grams.  14)29 students is 20% of 145 students.

 Given original amount and new amount  Need to find amount increase/decrease before finding percent increase/decrease  Use the same formula: Percent ∙ Base = Amount  To find percent increase or decrease, use the original amount as your base.

 The price of an item increases from $15 to $18. Find the percent increase.  Amount increase = $3  Base = $15 (original price)  Percent = unknown  Percent ∙ Base = Amount  x ∙ $15 = $3  Divide each side by $15  x = 0.2 = 20%

 3) Amount decrease = $10, Base = $48  $10 ÷ $48 = = 20.8%  4) Amount increase = 0.7 mi/gal, Base = 17.5 mi/gal  0.7 ÷ 17.5 = 0.04 = 4%  5) Amount increase = $4032, Base = $2498  $4032 ÷ $2498 = 1.61 = 161%  6) Percent decrease = 45% = 0.45, Base = 1200  Amount increase = (0.45)(1200) = 540 ; New number = 1200 – 540 = 660  7) Percent decrease = 25% = 0.25, Base = $16.50  Amount decrease = (0.25)($16.50) = $4.125  New price = $ $4.125 = $ ≈ $12.38 (the store gets half a cent)  8) Percent increase = 20% = 0.2, Base = $47.25  Amount increase = (0.2)($47.25) = $9.45  Bill total = $ $9.45 = $56.70

 Answer on a separate sheet of paper.  1.) Write 0.08% as a decimal and as a fraction.  2.) Write one-fifth as a decimal and as a percent.  3.) If a quantity doubles, what is the percent increase?