SSC CGL 6 06 2019 Shift 2 Paper

Question : 54 of 100

Marks: +1, -0

The average of thirteen numbers is 80. The average of the first five numbers is 74.5 and that of the next five numbers is 82.5. The 11

^{\th}

number is 6 more than the 12

^{\th}

number and the 12

^{\th}

number is 6 less than the 13

^{\th}

number. What is the average of the 11

^{\th}

and the 13

^{\th}

numbers?

Solution:

Average of 13 number

=80

First 5 number

=74.5

Next five no.

=82.5

=-5.5 \× 5+2.5 \× 5

=-27.5+12.5

=-15(15

is add in reamaning three no.)

)

Let

13^{ {\th }}

no.

=x

12^{ {\th }}

no.

=x-6

11^{ {\th }}

no.

=\ {x}

Sum of 3 number

=240+15

3 x-6=240+15

3 x=261

X=87

Average of

11^{ {\th }}

and

13^{ {\th }}

no.

=\ {87+87}/{2}

=87

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