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Mathematics 10 Online
OpenStudy (anonymous):

2/5 + 2/7

OpenStudy (mathstudent55):

To add fractions, you need a common denominator.

OpenStudy (mathstudent55):

What is the least common multiple of 5 and 7?

OpenStudy (anonymous):

5?

OpenStudy (anonymous):

is it 24/35

OpenStudy (mathstudent55):

5 is not a multiple of 7. You need a number that is a multiple of both 5 and 7. One way to find the smallest such number is to list the first several multiples of each number, 5 and 7, and find the smallest that appears in both lists.

OpenStudy (mathstudent55):

Yes, 35 is the LCM. \( \dfrac{2}{5} + \dfrac{2}{7} \) \(= \dfrac{2}{5} \times \dfrac{7}{7} + \dfrac{2}{7} \times \dfrac{5}{5} \) \(= \dfrac{14}{35} + \dfrac{10}{35} \) \(= \dfrac{24}{35} \)

OpenStudy (mathstudent55):

You are correct. 24/35 is the sum.

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