Question

81. The average age of 50 students in 10th std
class is 15 years. 10 more students are
admitted a fresh in the class and the average
age is increased by 0.5 years. The average age
of the newly joined students is​

Answer 1

Answer:

18 years

Step-by-step explanation:

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Answer 2

The average age of 10 newly joined students is 18 years.

Solution:

Given that average of 50 students is 15 years

When 10 more students are added average age is increased by 0.5 years which means average age of 50 + 10 = 60 students is 15+0.5 = 15.5 years

$\text { Average of age }=\frac{\text { Sum of age }}{\text { number of students }}$

$\text { Average of age of } 50 \text { students }=\frac{\text { Sum of ages of } 50 \text { students }}{50}$

Sum of ages of 50 students = Average of age of 50 students x 50

$= 15 \times 50 = 750$

Therefore sum of ages of 50 students= 750

$\text { Average age of } 60 \text { students }=\frac{\text { Sum of ages of } 60 \text { students }}{60}$

Sum of ages of 60 students = Average of age of 60 students x 60 = 15.5 x 60 = 930

Sum of ages of 10 newly joined student = Sum of ages of 60 students - Sum of ages of 50 students

=> Sum of ages of 10 newly joined student = 930 – 750 = 180  

Average age of 10 newly joined student = $\frac{180}{10} = 18$

Hence average age of 10 newly joined students is 18 years.