by Arianne Boynton 14 years ago
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The word percent comes from the Latin word per centum meaning out of 100.
They are a way of representing fractions with denominators of 100.
1. take off the percent sign
2. move the decimal place over to the LEFT two times
40% becomes .40
move the decimal place over two places to the RIGHT and add a percent sign
.30 becomes 30%
1. take off percent sign
2. move the decimal place two spaces to the LEFT
3. once it it is decimal form, look at the 100's place and put that number over 100
4. reduce if possible
1. 60%= 2. 0.60= 3. 60/100= 4. 60/100= 6/10= 3/5
fraction 1/2= (1 divided by 2)= .50 move the decimal place over 2 times and add a percent sign.
1/2=.50=50%
For any two ratios a/b and c/d,
a/b=c/d
Using the concept of porportions with percents, we can solve story problems.
Take this one for example: If4.8 pounds of flour costs $1.20, how much would 6 pounds cost?
Solution: Using the ratio of pounds to cost produces the following proportion, which x representing the cost for 6 pounds.
4.8/1.20=6/x
By the rule for equality of fractions, we obtain
4.8 x x =1.20 x 6
x=(1.20 x 6)/4.8
x= 1.5
therefore the cost of 6 pounds is $1.50
used when calculating the percent of something
Part
Whole
ex: If $880 of a $2000 loan is paid off, what percent is this?
Part 880 =
Whole 2000 .44 = 44%
A ratio os a pair of positive numbers that is used to compare two sets.
For any two positive numbers a and b, the ratio of a to b is the fraction a/b. This ratio is also written as a:b.
when we have a ratio, say "3 to 4", we are saying for every 3 of one thing we have four of the other.
For example lets think of a recipe that calls for 3 cups water 2 cups oil and 2 eggs. So for every 3 cups of water, we need 2 cups oil and 2 eggs. What if we were to say oops I forgot the eggs, would this make a difference? Lets think of it in terms of percents.
Lets say that these are the only three ingredients. If we forgot the eggs we would have missed 2 items out of the 7 mentioned (because there are 2 eggs needed). We could say that we missed 2/7, or 2:7 which equals .28571 or in percents approx. 28.6%. Therefore we can see that if 28.6% of our ingredients were missing, that is a big deal, so yes it was important to remember the eggs in the recipe.
