Question

The Average age of 20 students in a class is 16 yars.One student whose age is 18 years has left the class. Find out average age of rest of the students.

Answer 1

Given:
Mean, $\overline{\mathbf{X}}$ = 16 years
Number of observations, N= 20

We know,
$\overline{X}=\frac{\Sigma X}{N}$

ΣX of 20 students = ${\overline{X}}_{20}\times N$= 20 × 16 = 320
ΣX of 19 students = $\Sigma X_{20}-ageofthestudentwholefttheclass$=320 − 18 = 302

Thus, the average age of rest of the students is:

$\overline{\mathrm{X}}\mathrm{of}19\mathrm{students}=\frac{302}{19}=15.89years$

Hence, the correct average age is 15.89 years