Question

The average of a list of 4 numbers is 90. 0.A new list of 4 numbers has the same first 3 numbers as the original list, but the fourth numberin the list is 80, and the fourth number in the new list is 96. What is the average of this new list of numbers.

Answer 1

New Average of New List = 87.5

Explanation:

Average is the arithmetic mean (M) of observations.

M = ΣX / N

where ΣX = sum of all observations , N = number of observations

Given : M = 90 ; N = 40

M = ΣX / N

90 = ΣX / 4

ΣX = 90 x 4

ΣX = 360 [ Of Old List of 4 numbers ]

New ΣX of new list of 4th new number = Old ΣX - Old 4th No. + New 4th No.

New ΣX = 360 - 90 + 80

New ΣX = 350

New Average (Mean M) = New ΣX / N

New M = 350 / 4

New M = 87.5