Answer:
Given that
h = 110 m
Mass flow rate(m') = 900 kg/s
Mechanical power = 800 KW
Power generation = 750 KW
p = m' g h
P= 900 x 10 x 110
P= 990 KW
The turbine efficiency ηt
ηt = 800 /990
ηt = 0.808
Generator efficiency ηg
ηg= 750/800
ηg= 0.93
Combine efficiency η
η = ηt x ηg
η =0.75