Question

The arithmetic mean of 80 numbers is 55. If two numbers is namely 250 and 850 are removed, what is the arithmetic mean of the remaining numbers

Answer 1

The arithmatic mean of 80 numbers =X/80=55

Where X is the sum of the 80 numbers

X=80×55= 4400.

The arithmatic mean after removing the two numbers=

(X -250 -850)/78=(4400 - 250 -850)/78= 42.3

Notice that, 78 is the count of the numbers after removing two numbers.