Question

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

Mileage (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/litre. Do you agree with this claim?

Answer 1

Mileage (km/l)	Class marks `(bb(x_i))`	Number of cars `(bb(f_i))`	`bb(f_i x_i)`
10 – 12	11	7	77
12 – 14	13	12	156
14 – 16	15	18	270
16 – 18	17	13	221
Total		`sumf_i = 50`	`sumf_i x_i = 724`

Here, `sumf_i` = 50

And `sumf_i x_i` = 724

∴ Mean `(barx) = (sumf_i x_i)/(sumf_i)`

= `724/50`

= 14.48

Hence, mean mileage is 14.48 km/l.

No, the manufacture is claiming mileage 1.52 km/l more than average mileage.