Question

The average age of 12 students is 20 years.If the age of one more student is included ,the average decreases by 1.What is the age of the new student?

Answer 1

Answer:

Given :

$\tt {\frac {x_{1}+x_{2}...+x_{12}}{12} = 20}$

=》 $\tt {x_{1} + x_{2}...x_{12} = 240}$

Now, when the new student's age is added :

$\tt {\frac{x_{1} +x_{2}..x_{13}}{13} = 19}$

=》 $\tt {x_{1} + x_{2}...+x_{13} = 247}$

Subtract the sums :

247 - 240 = 7 years = age of new student