Question

The mean of 7observations is 20.If the mean of the first four observation is 18 and that of the last four is 22 .Find the fourth observation

Answer 1

$\textbf {Hey there, here is the solution.}$

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STEP 1 : Find the sum of the 7 observations:

mean of the 7 observations = 20

sum of the 7 observations = 20 x 7 = 140

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STEP 2: Find the sum of the first 4 observations:

mean of the first 4 observations = 18

Sum of the first 4 observations = 18 x 4 = 72

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STEP 3: Find the sum of the last 4 observations:

Mean of the last 4 observations = 22

Sum of the last 4 observations = 22 x 4 = 88

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STEP 4: Find the sum of the 8 observations:

Sum of the 8 observations = 72 + 88 = 160

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STEP 5: Find the 4th observations:

There were 8 observations because the 4th observations were counted twice

4th observation = 160 - 140 = 20

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Answer: The fourth observation is 20

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⭐$\textbf {Cheers}$⭐