The arithmetic mean of 5, 8, 10, 15, 24 and 28 is_______

Analyze the question: You are asked for the arithmetic mean (average) of six numbers.

Concept: Arithmetic mean = (sum of all values) ÷ (number of values)

Solution:

Step 1: Add the numbers 5 + 8 = 13 13 + 10 = 23 23 + 15 = 38 38 + 24 = 62 62 + 28 = 90

Sum = 90

Step 2: Count the values There are 6 numbers.

Step 3: Divide Mean = 90 ÷ 6 = 15

Checking the options:

• A (145): not possible, since it is larger than every number in the list.
• B (15): matches our result.
• C (90): this is the sum, not the mean. It is a common trap, because students forget to divide.
• D (6): this is the number of values, not the mean.

Answer: B (15)

Exam tip: The mean must always lie between the smallest and largest values (here, between 5 and 28). This lets you eliminate wrong options quickly. Also, be careful not to stop at the sum, because JAMB often includes the sum as a distractor option.