JAMB Mathematics 2023 Paper

Concept:The mean of grouped data is calculated using the class mark of each interval and its frequency.Explanation:Find the class mark of each age interval. For $5-6$, class mark $= \frac{5+6}{2} = 5.5$ For $7-8$, class mark $= \frac{7+8}{2} = 7.5$ For $9-10$, class mark $= \frac{9+10}{2} = 9.5$ Multiply each class mark by its corresponding frequency. $5.5 \times 29 = 159.5$ $7.5 \times 40 = 300.0$ $9.5 \times 38 = 361.0$ Find the totals. $\sum fx = 159.5 + 300.0 + 361.0 = 820.5$ $\sum f = 29 + 40 + 38 = 107$ Calculate the mean. Mean $= \frac{\sum fx}{\sum f} = \frac{820.5}{107}$ Mean $= 7.668\ldots \approx 7.7$Answer:The mean age is $7.7$ years. Therefore, the correct option is A.