Answer: D 205
Step-by-step explanation:
Let,
Number of all trouts = N
Number of speckled trouts = Ns = 645
Number of rainbow trouts = Nr
Number of male speckled trouts = Ms
Number of female speckled trouts = Fs
Number of male rainbow trouts = Mr
Number of female rainbow trouts = Fr
Since, Ms = 2Fs + 45
Also, Ms + Fs = 645
Therefore, 2Fs + 45 + Fs = 645
Fs = (645-45)/3 = 200
Female speckled trouts = 200
Since
Ms + Fs = 645
Ms = 645- 200 = 445
Since, Fs/Mr = 4/3
Mr = 3x200/4 = 150
Since,
Mr/N = 3/20
N = 20x 150/3 = 1000
Recall that,
N = Ms+Fs+Mr+Fr
Fr = N-Ms-Fs-Mr
Fr = 1000-445-200-150
Fr = 205
Therefore, the number of rainbow female trouts = 205