\(\begin{array}{c|c} x & 2 & 4 & 6 & 8\\ \hline f & 4 & y & 6 & 5 \end{array}\)

If the mean of the above frequency distribution is 5.2, find y

  • A 2, 1
  • B 1, 2
  • C 1, 5
  • D 5, 2
jamb 1992mathematics

The correct answer is C. 1, 5

Mean \(\bar{x}\) = \(\frac{\sum fx}{\sum f}\)

= \(\frac{5.2}{1}\)

= \(\frac{8 + 4y + 36 + 40}{4 + y + 6 + 5}\)

= \(\frac{5.2}{1}\)

= \(\frac{84 + 4y}{15 + y}\)

= 5.2(15 + y)

= 84 + 4y

= 5.2 x 15 + 5.2y

= 84 + 4y

= 78 + 5.2y

= 84 = 4y

= 5.2y - 4y

= 84 - 78

1.2y = 6

y = \(\frac{6}{1.2}\)

= \(\frac{60}{12}\)

= 5

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