ACT Math : How to add fractions

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #1 : How To Add Fractions

Add the following fractions

Possible Answers:

Correct answer:

Explanation:

To add fractions you first must find the lowest common denominator. For these fractions it is 60. Then you must multiply the numerator and denominator by the number such that the denominator is equal to the LCD. For example  gets multiplied by 12 (on both the numerator and denominator) because 5 times 12 is 60. When you do that you get the expression

then you just add the numerators and get

2 goes into both of those numbers so you get

 

Example Question #2 : How To Add Fractions

 

Simplify the expression:

Possible Answers:

Correct answer:

Explanation:

First you want to find the least common denominator (in this case it's 18): 

Example Question #3 : How To Add Fractions

What is the result of adding  of  to ?

Possible Answers:

Correct answer:

Explanation:

Let us first get our value for the percentage of the first fraction. 20% of 2/7 is found by multiplying 2/7 by 2/10 (or, simplified, 1/5): (2/7) * (1/5) = (2/35)

Our addition is therefore (2/35) + (1/4). There are no common factors, so the least common denominator will be 35 * 4 or 140. Multiply the numerator and denominator of 2/35 by 4/4 and the numerator of 1/4 by 35/35.

This yields:

(8/140) + (35/140)  = 43/140, which cannot be reduced.

Example Question #3 : How To Add Fractions

Which of the following is equal to ?

Possible Answers:

Correct answer:

Explanation:

We have two options here. We can manipulate the answers to work backwards and find a common denominator. This involves simply subtracting or adding two fractions. We can also try to rewrite the numerator by adding and subtracting the value . This serves the purpose of creating a sum in the numerator than can be split into  and . This gives us one of the factors in the denominator in each numerator. When we separate or decompose the fraction, we can divide out by the common factor to re-express this as the difference of two rational expressions. 

 

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