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Insert three fractions between $\frac1/4$ and $\frac1/2$ so the five fractions form an arithmetic sequence. What is the sum, expressed as a common fraction, of these three new fractions?

 Jan 15, 2021

Best Answer 

 #1
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Do you mean this problem:

 

Insert three fractions between $\frac14$ and $\frac12$ so the five fractions form an arithmetic sequence. What is the sum, expressed as a common fraction, of these three new fractions?

 

If you do then the answer is 9/8

 

this is the reasoning:

 

The term in the middle is the arithmetic mean of $\dfrac{1}{4}$ and $\dfrac{1}{2}$, or $\dfrac{3}{8}$, so the arithmetic sequence looks like $$\dfrac{1}{4}, \underline{\qquad} , \dfrac{3}{8}, \underline{\qquad} , \dfrac{1}{2}.$$The fraction $\dfrac{3}{8}$ is also the arithmetic mean of the two missing terms, and thus $\dfrac{3}{8}$ is the average of the $3$ new fractions. So, their sum is $3\cdot\dfrac{3}{8}=\boxed{\dfrac{9}{8}}$.

 Jan 15, 2021
 #1
avatar
+1
Best Answer

Do you mean this problem:

 

Insert three fractions between $\frac14$ and $\frac12$ so the five fractions form an arithmetic sequence. What is the sum, expressed as a common fraction, of these three new fractions?

 

If you do then the answer is 9/8

 

this is the reasoning:

 

The term in the middle is the arithmetic mean of $\dfrac{1}{4}$ and $\dfrac{1}{2}$, or $\dfrac{3}{8}$, so the arithmetic sequence looks like $$\dfrac{1}{4}, \underline{\qquad} , \dfrac{3}{8}, \underline{\qquad} , \dfrac{1}{2}.$$The fraction $\dfrac{3}{8}$ is also the arithmetic mean of the two missing terms, and thus $\dfrac{3}{8}$ is the average of the $3$ new fractions. So, their sum is $3\cdot\dfrac{3}{8}=\boxed{\dfrac{9}{8}}$.

Guest Jan 15, 2021
 #2
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Very nice, guest  !!!!

 

 

cool cool cool

CPhill  Jan 15, 2021

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