WAEC Mathematics 2022 Paper

Concept:The lower quartile is the median of the lower half of the data. First, arrange the data in ascending order, then find the required position.Explanation:Arrange the ages in ascending order:$$12,\;13,\;15,\;36,\;39,\;41,\;41,\;43,\;43,\;47,\;49$$The total number of data items is $n = 11$.Since the number of items is odd, use:$$\text{Lower quartile position} = \frac{n+1}{4}$$Substitute $n = 11$:$$\frac{11+1}{4} = \frac{12}{4} = 3$$So the lower quartile is the $3$rd value in the ordered list.The $3$rd value is $15$.Answer:The lower quartile is $15$.Correct option: C. $15$.