University:
California State University, Northridge
Course:
MATH 102 | Pre-Calculus I
Academic year:

2024
Views:

371

Pages:

4
Author:

maturizeznhr

Percent is another method of expressing fractions or parts of any object. Percents are expressed in terms of hundredths, so 100% means 100 hundredths or 1. i.e. Percent (per hundred) -A number divided by 100 (written with a % symbol behind it) What does 65% mean (Always reduce the fraction) From this chapter you will want to study the methods of converting fractions to decimals and percents . You will also need to know how to convert from percents to fractions and decimals. Fractions ⇒ Decimals Example: , we do division to get a decimal = 1.6 ( see Mod. III) If it is a mixed number, keep the integer and convert the improper fraction to decimal, then put them together. Example: , do the division so the answer is 3.4 Decimals ⇒ Fractions Example: 2.125 we have three decimal places so we use 1000 (with three 0) as denominator ⇒ 2.125 = lowest term.) (Always reduce fraction to the Percent ⇒ Fraction Put Example: Example: and drop % sign, reduce if necessary Example: Fraction ⇒ Percent Set fraction = Example: and solve for x as decimal and add % sign , cross-multiplying to get 8x = 300 ⇒ Don't forget add % behind the number, the answer is OR: Multiply the fraction by , it is equivalent to multiply by 1, then switch the 100 from the denominator to the side as a % symbol and multiply the fraction by 100. Example: Percent ⇒ Decimal If the percent already has a decimal point then move it two places to the left and drop % sign Example: 20.3% = 0.203 Example: 0.78% = 0.0078 If it does not have a decimal point, then put one at the end of the last digit and then move it two places to the left and drop % sign Example: 5% = 5.% = 0.05 Decimal or Whole # ⇒ Percent If it already has a decimal point then move it two places to the right and add % sign. Example: 0.056 = 5.6% If it does not have a decimal point then put one at the end of the last digit and then move it two places to the right and put % sign Example: 32 = 32. = 3200% OR: Multiply the decimal by , it is equivalent to multiply by 1, then switch the 100 from the denominator to the side as a % symbol and multiply the decimal by 100. Example: Example: Word problems concerning percents come in the following varieties: 1. What is x percent of y ? 2. x is what percent of y ? Each can be solved using ratios but the set up of the ratios will be different depending on the type of question presented . If we want to know what 15% of 130 is we set up the following ratio: In the second type of problem we see the words 'what percent' which translate to ?/100 . For example if we the question reads '7 is what percent of 49 ?' we set up the following ratio: Some of the more interesting percent problems involve sale prices . For example: If a dress is purchased for 186.00 on sale at a 20% discount what was the original price of the dress ? One way to approach this problem is to look at the $186.00 purchase price as it relates to the original price . 186.00 is 20% less than the original price therefore it can also be thought of as 80% of the original price (think of the original price as the 100% price). x in this ratio represents the original price .