The traffic police recorded the speed (in km/h) of 10 motorists as 47, 53, 49, 60, 39, 42, 55, 57, 52, 48. Later on an error in recording instrument was found. Find the correct overage speed of the motorists if the instrument recorded 5 km/hr. less in each case.
The speed of 10 Motorist are:
47, 53, 49, 60, 39, 42, 55, 57, 52, 48
Later on it was discovered that the instrument recorded 5 km/h less than in each case
Therefore, correct values are = 52, 58, 54, 65, 44, 47, 60, 62, 57, 53
Therefore, correct mean = 
= 
= 55.2 km/h
15