In a tree 3/5 of the birds are robins while the rest are bluejays. If

Let total no of birds=100
Robins=60
Bluejays=40
Male Robins=45, Female robins=15
Male Bluejays=10
Female Bluejays=30
Required fraction=55/100=11/20
Answer C

800score Official Solution:

First we need to determine the fraction of the birds that are bluejays:
(fraction that are bluejays) = 1 (total birds) – 3/5 (fraction that are robins) = 5/5 (total birds) – 3/5 (fraction that are robins) = 2/5
Next, determine the fraction of all the birds that are female:
(fraction of all birds that are female) = (3/5) × (1/4) (female robins) + (2/5) × (3/4) (female bluejays) = 3/20 (female robins) + 6/20 (female bluejays) = 9/20 of all birds are female.
The fraction of male birds then is:
(fraction of all birds that are male) = 1 (total birds) – 9/20 (female birds) = 20/20 (total birds) – 9/20 (female birds) = 11/20 of all birds are male.

The alternative way:
Suppose there were 100 birds in the tree. Using the fractions in the question, you can fill up this table.



Therefore 55 out of 100 birds are male, implying a fraction of
55/100 = 11/20.

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