SAT Math : Lowest Common Denominator
Study concepts, example questions & explanations for SAT Math
All SAT Math Resources
Example Questions
Example Question #131 : Arithmetic
3/5 + 4/7 – 1/3 =
88/105
4/3
72/89
7/9
3/37
88/105
We need to find a common denominator to add and subtract these fractions. Let's do the addition first. The lowest common denominator of 5 and 7 is 5 * 7 = 35, so 3/5 + 4/7 = 21/35 + 20/35 = 41/35.
Now to the subtraction. The lowest common denominator of 35 and 3 is 35 * 3 = 105, so altogether, 3/5 + 4/7 – 1/3 = 41/35 – 1/3 = 123/105 – 35/105 = 88/105. This does not simplify and is therefore the correct answer.
Example Question #1 : How To Find The Lowest / Least Common Denominator
What is the lowest common denominator of the fractions below?
In order to find the lowest common denominator, you must first list the multiples of each of the denominators of the three fractions:
The lowest common denominator between these three sets of multiples is 
Example Question #2 : Lowest Common Denominator
What is the Lowest Common Denominator of 
The smallest number they all have in common in 
All SAT Math Resources
