Find the co-efficient of variation of a sample which has mean equal to 25 and standard deviation of 5.

When coefficient of variation is 50 and standard deviation is 10 then mean is _____.

Calculate co-efficient of variation of marks secured by a student in the exam, where the marks are : 85, 91, 96, 88, 98, 82

A group of 65 students of class XI have their average height is 150.4 cm with coefficient of variance 2.5%. What is the standard deviation of their height?