Question

The average of a class of 20 boys is15 years. If eight boys of 18 years average join the class. Find the new average of the class
d) 15.86
c) 20
a) 18.6
b) 17 yrs
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Answer 1

Answer:

d

d is the correct answer

Step-by-step explanation:

I hope it will help you

Answer 2

Answer:

The average age of 20 students is 12 years.

∴ Total age of 20 students =20×12=240years

It is given that, student who is 10years old left the class.

∴ Total age of 19 students =240−10=230years

An then 2 new students entered and average remain same.

∴ Total age of 21 students =21×12=252years

⇒ Total age of 2 new students who entered in the class =252−230=22years

Let x and y be the two new students.

∴ x+y=22 ------ ( 1 )

According to the question,

x−y=4 ----- ( 2 )

Now adding (1) and (2), we get,

x=13

Putting value of x in equation ( 1 ) we get,

y=9

∴ The age of younger one is 9years.

I hope friends you can understand it