WAEC Further Mathematics 2011 Paper

Concept:Use the given mean to find the unknown value $x$, then arrange the data to locate the middle value.Explanation:The mean of the five numbers is $6$. So, write the mean equation: $$\frac{2 + 5 + (x+2) + 7 + 9}{5} = 6$$ Simplify the numerator: $$2 + 5 + x + 2 + 7 + 9 = x + 25$$ Thus, $$\frac{x + 25}{5} = 6$$ Multiply both sides by $5$: $$x + 25 = 30$$ Subtract $25$ from both sides: $$x = 5$$ Now find the third number: $$x + 2 = 5 + 2 = 7$$ The full data set is: $2, 5, 7, 7, 9$. Arrange in ascending order: $2, 5, 7, 7, 9$. Since there are $5$ numbers, the median is the $3$rd value. The $3$rd value is $7$.Answer:Median $= 7.0$ Correct option: D. 7.0