WAEC Mathematics 2021 Paper

Concept:The first quartile is the value below which $25\%$ of the data lies.Explanation:Arrange the data in increasing order: $6, 7, 7, 7, 8, 8, 8, 9, 9, 11$.There are $n = 10$ values.For ungrouped data, the position of the first quartile is given by $\frac{n+1}{4}$.So, position $= \frac{10+1}{4} = \frac{11}{4} = 2.75$.This means the first quartile lies between the 2nd and 3rd values.The 2nd value is $7$ and the 3rd value is also $7$.Hence, the first quartile is $7.0$.Answer:B. $7.0$