Question

From the following cumulative frequency table, draw ogive and then use it to find:

1. Median 
2. Lower quartile 
3. Upper quartile 

Marks (less than)	10	20	30	40	50	60	70	80	90	100
Cumulative frequency	5	24	37	40	42	48	70	77	79	80

Answer 1

Marks (less than)	Cumulative frequency
10	5
20	24
30	37
40	40
50	42
60	48
70	70
80	77
90	79
100	80

Number of terms = 80

Median = 40^th term 

i. Median = Through 40^th term mark draw a line parallel to the x-axis which meets the curve at A. From A, draw a perpendicular to x-axis which meets it at B. 

Value of B is the median = 40 

ii. Lower quartile (Q₁) = 20^th term = 18

iii. Upper quartile (Q₃) = 60^th term = 66