Answer:
The number of boys, x = 12
Step-by-step explanation:
Given that the sum of the ages of the boys in a class = 84 years
The number of boys = x
A new boy aged 8 years 1 month is added and the average age increases by 1 month
We have
Average age = 84/x = y
Age of new boy = 8 years 1 month = [tex]8\frac{1}{12} \ year[/tex]
New average = y + 1/12 = [tex](8\frac{1}{12}+84) /(x + 1)[/tex] which gives;
84/x + 1/12 = [tex](8\frac{1}{12} + 84) /(x + 1)[/tex]
[tex]\dfrac{x +1008}{12 \cdot x} = \dfrac{1105}{12 \cdot x+ 12}[/tex]
(x + 1008)×(12·x + 12) = 1105× 12·x
12·x² -1152·x + 12096 = 0
x² -96·x + 1008 = 0
(x - 84)×(x - 12) = 0
Therefore, x = 12 or 84,
The number of boys are 12 or 84
For there to bee 84 boys, their average age would be one year each
Given that they are boys not babies, then there are only 12 boys.
