SAT Math : Compound Fractions
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Example Question #1 : Compound Fractions
4/5 + 7/3 + 9/30 = ?
30 / 100
103 / 30
20 / 38
80 / 30
20 / 30
103 / 30
To add fractions you must first find the lease common denominator, that is, a number that all of the denominators (the bottom number) can divide into.
In this case, 5, 3, and 30, both 5 and 3 divide successfully into 30, so 30 is the least common denominator.
Now divide each smaller denominator into thirty. Then multiple the answer by the top number:
5/30 = 6
Therefore 4/5 = 4*6 / 5*6 = 24/30
3/30 = 10
Therefore 7*10 / 3*10 = 70/30
Then add all the numerators together:
24/30 + 70/30 +9/30 = (24+70+9)/30 = 103 / 30
Example Question #2 : Compound Fractions
The student body of a high school is 1/4 boys, and 2/3 of the boys are seniors. If 1/18 of the senior boys were accepted into Harvard, which of the following could be the total number of students in the class?
90
148
108
15
54
108
For this problem it would be easier to choose one of the answers and go from there. 108 works because 1/4 of 108 is 27 then 2/3 of 27 is 18 and 1/18 of 18 is 1, which makes this answer possible.
The other answers come out with a remainders that make no sense, since a fractional part of a person cannot have been accepted to a school.
Example Question #2 : How To Find A Solution To A Compound Fraction
Compute:
Rewrite each fraction into an improper fraction.
The common denominator is 16.
The correct answer is:
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