Question

Observe the frequency polygon and complete the table.

Class	18 – 19	19 – 20	20 – 21	21 – 22	22 – 23	23 – 24
Class mark	18.5	`square`	20.5	21.5	`square`	23.5
Frequency	4	13	15	19	17	6
Coordinates of points	(18.5, 4)	(19.5, 13)	`square`	(21.5, 19)	`square`	(23.5, 6)

Answer 1

For class 19 – 20:

Class mark: `(19 + 20)/2` = 19.5

For class 20 – 21:

Coordinates of points: (20.5, 15)

For class 22 – 23:

Class mark: `(22 + 23)/2` = 22.5

Coordinates of points: (22.5, 17)

Class	18 – 19	19 – 20	20 – 21	21 – 22	22 – 23	23 – 24
Class mark	18.5	\[\boxed{19.5}\]	20.5	21.5	\[\boxed{22.5}\]	23.5
Frequency	4	13	15	19	17	6
Coordinates of points	(18.5, 4)	(19.5, 13)	\[\boxed{(20.5, 15)}\]	(21.5, 19)	\[\boxed{(22.5, 17)}\]	(23.5, 6)