Question 827719
For the juniors:
average = ( sum of their scores ) / ( number of juniors )
Sum of their scores = ( average )x( number of juniors )
Sum of their scores = {{{ 80*35 }}}
------------------------------
For the seniors:
average = ( sum of their scores ) / ( number of seniors )
Sum of their scores = ( average )x( number of seniors )
Sum of their scores = {{{ 70*15 }}}
-----------------------------
Average for all the students:
( sum of scores of both juniors and seniors ) / ( number of juniors and seniors )
{{{ ( 80*35 + 70*15 ) / 50 }}}
{{{ ( 2800 + 1050 ) / 50 }}}
{{{ 3850 / 50 = 77 }}}
the answer is (D)