Question

A class contains 8 students where the sum of all their heights is 1024 cm. A kid who is 149 cm tall leaves the class. What is the difference between the old average height and the new average height?

• A.
  2 cm
• B.
  5 cm
• C.
  1 cm
• D.
  3 cm

Answer 1

The correct option is D

3 cm
The previous sum of all the heights is 1024 cm.
Therefore, the previous average is:

$=\frac{Sumofallobservations}{Totalnumberofobservations}$

$=\frac{1024}{8}$

$=128cm$

Since 1 kid left,
New sum = 1024 - 149 = 875 cm
New number of observations = 8 - 1 =7

$\therefore$ New Average $=\frac{875}{7}$

$\Rightarrow$ $125cm$

$\therefore$ Difference between the averages is 128 -125 = 3 cm

Hence, 3 is the required answer.