Question 1: Calculate the mean of the numbers 12, 15, 20, and 25. Show your working.

Answer: 18

Question 2: A class of 30 students has an average height of 150 cm. If one student with a height of 160 cm joins the class, what is the new average height? Show your working.

Answer: 149.67

Question 3: The numbers 8, 12, 15, and 20 are given. A student mistakenly calculates the mean as 18. Identify and correct the mistake.

Answer: The sum is 55, and the mean is 55/4=13.75, not 18.

Question 4: Plot the graph of y=2x for x values from 0 to 5 on the grid.

Answer: See full answer key

Question 5: A factory produces 200, 250, 300, and 350 units of product daily. Find the average number of units produced daily. Show your working.

Answer: 275

Question 6: A student calculates the mean of 10, 12, 14, 16, and 18 as 14. Is this correct? If not, find the correct mean and explain the mistake.

Answer: Sum=70, mean=14, which is correct; no mistake.

Question 7: A basketball team scored 80, 85, 78, 90, and 88 points in five games. What is their average score?

Answer: 84.2

Question 8: Identify the mistake if a student finds the mean of 5, 10, 15 as 20.

Answer: Sum is 30; mean=30/3=10, not 20.

Question 9: A group of 40 people has an average age of 35 years. When a new person aged 50 joins, what is the new average age? Show your working.

Answer: 34.75

Question 10: A set of numbers has a mean of 20. If one number is 10, and the mean of the remaining numbers is 22, how many numbers are in the set?

Answer: 6

Question 11: A student claims that if the mean of three numbers is 10, then their total sum must be 30. Is this always true? Explain your reasoning.

Answer: Yes, because mean=total sum divided by number of values. Total sum=mean×number=10×3=30.