Calculate the mean of the scores of 20 students in a Mathematics test.

Marks	10-20	20-30	30-40	40-50	50-60
Number of students	2	4	7	6	1

4

(a)

Determine the mean of the following distribution.

Marks	Number of students
Below 10	5
Below 20	9
Below 30	17
Below 40	29
Below 50	45
Below 60	60
Below 70	70
Below 80	78
Below 90	83
Below 100	85

4

(a)

An aircraft has 120 passenger seats. The number of seats occupied during 100 flights is given in the following table:

Number of seats	100-104	104-108	108-112	112-116	116-120
Frequency	15	20	32	18	15

Determine the mean number of seats occupied over the flights.

4

(a)

The mileage (in km/L) of 50 cars of the same model was tested by a manufacturer and details are tabulated as given below:

Mileage (in km/L)	10-12	12-14	14-16	16-18
Number of cars	7	12	18	13

Find the mean mileage. The manufacturer claimed that the mileage of the model was 16 km/L. Do you agree with this claim?

4

(a)

The mean of the following frequency distribution is 50, but the frequencies f₁ and f₂ in classes 20-40 and 60-80 respectively are missing. Find the missing frequencies.

Class interval	0-20	20-40	40-60	60-80	80-100	Total
Frequency	17	f1	32	f2	19	120

4

(a)