Question

The students of three classes X, Y and Z wrote a

test. The average marks of the students of X, Y and

Z are 70, 81 and 90 respectively. The average

marks of the students of X and Y is 76. The average

marks of the students of Y and Z is 86. Find the

average marks of the students of all the three

classes to the nearest integer.​

Answer 1

Answer:

According to question

(i)

x+y

83x+76y

=79

⇒x=

4

3y

(ii)

y+z

76y+85z

=81

Z=

4

5y

Average of all 3=

x+y+z

83x+76y+85z

=

4

3y

+y+

4

5y

83(

4

3y

)+76y+85

4

(85)

⇒

4

3

+1+

4

5

4

249

+76+

4

425

=

4

3+4+5

4

249+304+425

=

12

978

=81.5.