Checkpoint: missing numbers, gaps and running totals

Class marks 5, 15 and 25 have frequencies 3, f and 5. The mean is 17. What is f?

• 2
• 8
• 4

The total is 30. The frequencies are 5, x, 8 and y. What is x + y?

• 13
• 17
• 22

The total is 50. What value does n ÷ 2 have in the median formula?

• 25
• 5
• 50

Classes 5-9 and 10-14 leave a gap of 1. What are they after the gap is closed?

• 5-9.5 and 9.5-14
• 4.5-9 and 10-14.5
• 4.5-9.5 and 9.5-14.5

Below 10: 7 readings. Below 20: 19 readings. How many are in the class 10-20?

• 12
• 19
• 7