Mean

What is the mean deviation of first 10 even natural numbers?

The frequency distribution of the marks obtained by students in a Science examination is given below: 

Direction for Questions (95-96): Consider the following for the two (02) items that follow: The sum and the sum of squares of the observation corresponding to length X (in cm) and weight Y (in gm) of 50 tropical tubers are given as ∑X = 200, ∑Y = 250, ∑X² = 900 and ∑Y² = 1400.

 Which one of the following statements is correct?

What is the arithmetic mean of 8², 9², 10²,... 15²?

The arithmetic mean of 100 observations is 50. If 5 is subtracted from each observation and then divided by 20, then what is the new arithmetic mean?