#### 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/I) 10-20 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?

Solution.  Here we calculate mean by following
1.Find the mid point of each interval.
2.Multiply the frequency of each interval by its mid point.
3.Get the sum of all the frequencies (f) and sum of all the (fx)
4.Now divide sum of (fx) by sum of (f)

 MIleage (km/I) No.of cars (fi) xi fixi 10-12 7 11 77 12-14 12 13 156 14-16 18 15 270 16-18 13 17 221 $\sum f_{i}= 50$ $\sum f_{i}x_{i}= 724$

$mean\left ( \bar{x} \right )= \frac{\sum f_{i}x_{i}}{\sum f_{i}}= \frac{724}{50}= 14\cdot 48 \ \ km/L$