If the mean of 5 observations x, x + 2, x + 4, x + 6 and x + 8 is 11, then the mean of the last three observations is:
Solution
Correct Answer: Option B
Solution:
প্রশ্নটিতে বলা হচ্ছে যে, x, x + 2, x + 4, x + 6, এবং x + 8 এর গড় 11 হলে শেষের 3 টি সংখ্যার গড় কত ?
প্রশ্ন অনুযায়ী, \(\frac{{x + x + 2 + x + 4 + x + 6 + x + 8}}{5}\) = 11
=> \(\frac{{5x + 20}}{5}\) = 11
=> 5x + 20 = 55
=> 5x = 55 - 20 = 35
=> x = \(\frac{{35}}{5}\) = 7
অতএব শেষের 3 টি সংখ্যা হলো x + 4 = 7 + 4 = 11
x + 6 = 7 + 6 = 13
x + 8 = 7 + 8 = 15
অতএব, এদের গড় হলো = \(\frac{{11 + 13 + 15}}{3} = \frac{{39}}{3}\) = 13
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