SAT Math : Percentage
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Example Questions
Example Question #2011 : Psat Mathematics
Write as a fraction: 22%
4/9
4/7
2/3
11/100
11/50
11/50
22% = 22/100
Divide everything by 2:
22/100 = 11/50
11 is a prime number, so this is as reduced as this fraction can get.
Example Question #1 : Fractions And Percentage
When y is decreased by ten percent, the result is equal to fifteen percent of x. Assuming both x and y are nonzero, what is the ratio of x to y?
6
1/3
3
18
1/6
6
The problem states that decreasing y by ten percent gives us the same thing as taking fifteen percent of x. We need to find an expression for decreasing y by ten percent, and an expression for fifteen percent of x, and then set these two things equal.
If we were to decrease y by ten percent, we would be left with ninety percent of y (because the percentages must add to one hundred percent). We could write ninety percent of y as 0.90y = (90/100)y = (9/10)y. Remember, when converting from a percent to a decimal, we need to move the decimal two places to the left.
Similarly, we can write 15% of x as 0.15x = (15/100)x = (3/20)x.
Now, we set these two expressions equal to one another.
(9/10)y = (3/20)x
Multiply both sides by 20 to eliminate fractions.
18y = 3x
The question asks us to find the ratio of x to y, which is equal to x/y. Thus, we must rearrange the equation above until we have x/y by itself on one side.
18y = 3x
Divide both sides by 3.
6y = x
Divide both sides by y.
6 = x/y
Thus, the ratio of x to y is 6.
The answer is 6.
Example Question #2012 : Psat Mathematics
Write 7.5% as a fraction.
First convert the percentage to a decimal:
7.5% = .075
Then turn this into a fraction:
.075 = 75/1000
Simplify by dividing the numerator and denominator by 25:
75/1000 = 3/40
Example Question #2013 : Psat Mathematics
25% of 64 is equal to 5% of what number?
108
320
112
90
94
320
25% of 64 is 16 (you can find this with a calculator by 0.25 * 64). Divide 16 by 0.05 (or 1/20) to get the value of the number 16 is 5% of. (Or mental math of 16 * 20)
Example Question #1 : Percentage
Turn the following percentage into a fraction:
Since a percentage is a "part of 100" to turn it into a fraction we take the original number in the percent and place it over 100:
From here, simplify the fraction as necessary:
Example Question #1 : Percentage
Turn the following percentage into a fraction:
Since a percentage is a "part of 100" to turn it into a fraction we take the original number in the percent and place it over 100:
From here, simplify the fraction as necessary:
Example Question #3 : Percentage
Turn the following percentage into a fraction:
Since a percentage is a "part of 100" to turn it into a fraction we take the original number in the percent and place it over 100:
From here, simplify the fraction as necessary:
Example Question #4 : Percentage
Turn the following percentage into a fraction:
Since a percentage is a "part of 100" to turn it into a fraction we take the original number in the percent and place it over 100:
From here, simplify the fraction as necessary:
Example Question #5 : Percentage
Turn the following percentage into a fraction:
Since a percentage is a "part of 100" to turn it into a fraction we take the original number in the percent and place it over 100:
From here, simplify the fraction as necessary:
Example Question #6 : Percentage
Turn the following percentage into a fraction:
Since a percentage is a "part of 100" to turn it into a fraction we take the original number in the percent and place it over 100:
From here, simplify the fraction as necessary:
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