Question 598372
Total candidates = 50
average of 35 (juniors) candidates = 80
So the sum of the marks attained by juniors = 80*35 = 2800

average of 15 (senior) candidates = 70
the sum of the marks attained by seniors = 70*15 = 1050

Total marks attained by all the candidates (seniors & juniors) = 2800 + 1050
= 3850


average score for all 50 candidates = 3850/50 = 77


That's it.....