Question

The average height of 5 students is 150 centimetres. One more student of height 120 centimetres joins the group. find the new average height.​

Answer 1

The average height of 15 students of class six = 140

and the average height of 10 students of class seven = 145

So, average her height of both classes = (15*140+10*145)/15+10

(2100+1450)/25

3550/25 = 142 cm Ans.

by this method you can do your sum

Answer 2

Given

x

=

5

∑x

i

=150

⇒

i=1

∑

5

x

i

=750....(i)

5

∑x

i

2

−(

x

)

2

=18

5

∑x

i

2