Question

the avarage age of group of students in 15 years. when 5 more students joined the group the avarage age rose 1 year. the avarage age of the new students is.​

Answer 1

Answer:

Explanation:

average= sum of observations/total number of observation.

in given question,

average=15

let,

sum of observations ie., sum of ages of students of class be x and total number of observation ie., number of students=y

average= sum of observations/total number of observation.

so,

x/y=15---------------equation 1

it is also given that,

if another 5 students join average increase by 1 ie., new average is 16.

Let,

sum of ages of 5 students be z.

Now,

sum of observations=x+z

total number of observation=y+5.

New average= x+z/y+5=16-----------equation 2

We know,

x/y=15

so x=15y-------------equation 3

We also know,

x+z/y+5=16

so x+z=16(y+5)

x+z=16y+80---------------equation 4

Now substitute value of x from equation 3 in equation 4,

so,

x+z=16y+80

15y+z=16y+80

z=16y-15y+80

z=y+80---------equation 5

average of age of new 5 students=z/5=y+80/5.