Question

2. The average of the students of a class is 12 years. The average age of 15 of them is
10 years and the average age of the remaining is 13 years. How many students are
there in the class?
(1) 35 (2) 40 (3) 45 (4) 50​

Answer 1

Answer:

Step-by-step explanation:

Let the total number of students in the class be "x",

We know( formula ),

Average = ( sum of quantities ) / ( number of quantities )

According to the question, average age of students of the class is 12 years,

So,

= >  12 years = ( sum of ages of all students in years ) / x

= >  12 x = sum of ages of all students

Also, average age of 15 of them is 10 years,

= >  10 = ( sum of ages of 15 students ) / 15

= >  150 = sum of ages of 15 students

Average age of remaining students  is 13 years,

= >  13 = ( sum of ages of all students - 150 ) / ( x - 15 )

= >  13( x - 15 ) = ( 12x - 150 )

= >  13x - 195 = 12x - 150

= >  13x - 12x = 195 - 150

= >  x = 45

Therefore the total number of students in the class is 45.