Subtraction of two fractions. I'm learning math by reading books only and the book I'm currently s

ziphumulegn 2022-07-04 Answered
Subtraction of two fractions.
I'm learning math by reading books only and the book I'm currently studying is Smart Math by Marcia Learner in which I practice basic operation on fractions. I can't solve the two following problems. Let me show you how I did it but my answers don't match the answers the book presents.
1. 7 / 8 ( 1 / 3 ) = ?
7 / 8 X 3 / 3 = 21 / 24 and 1 / 3 X 8 / 8 = 8 / 24 21 / 24 + 8 / 24 = 13 / 24
My answer is 13 / 24 but, according to the book the answer is 1 / 2
2. 12 / 13 ( 3 / 7 ) = ?
84 / 91 ( 39 / 91 ) 84 / 91 + 39 / 91 = 123 / 91
Book's answer is 105 / 14
Please tell me where I've done the mistakes. I correctly did the other problems of similar kind but couldn't understand where I've done wrong.
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Answers (1)

amanhantmk
Answered 2022-07-05 Author has 17 answers
When adding or subtracting fractions, the denominators of the terms need to be the same.
First let's simplify the number of signs:
7 8 ( 1 3 ) = 7 8 + 1 3 = 1 3 7 8 .
Then we'll make the denominators the same by multiplying top and bottom by the same number on each term separately:
1 3 7 8 = 1 8 3 8 7 3 8 3 = 8 24 21 24 .
Now we can subtract the numerators straight away:
8 24 21 24 = 8 21 24 = 13 24 .
So you almost got it except for the sign.
Do the same thing with the second problem.
Did you like this example?
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