Answer:
The sum of ages of all 18 pupils in the class = 81
Step-by-step explanation:
Total number of pupil in the class = 18
Average of years in the class = [tex]4\frac{1}{2}[/tex]
Now, [tex]4\frac{1}{2} = 4 + \frac{1}{2} = 4 + 0.5 = 4.5[/tex]
⇒Average of sum of ages in the class = 4.05
Let us assume the sum of ages of all students in the class = m
By the formula for AVERAGE:
[tex]\textrm{Average of n obseravtions} = \frac{\textrm{Sum of n observations}}{\textrm{n}}[/tex]
[tex]\implies 4.5 = \frac{m}{18}[/tex]
or, m = 18 x 4.5 = 81
Hence, the sum of ages of all 18 pupils in the class = 81
