Question

# In a class, $$10%$$ of the girls have blue eyes, and $$20%$$ of the boys have blue eyes. If the ratio of girls to boys in the class is $$3:4$$, then what is the fraction of the students in the class having blue eyes?

A
11/70
B
11/45
C
14/45
D
12/33
E
23/49

Solution

## The correct option is A $${ 11 }/{ 70 }$$  $$\text{Let total number of students be 100}$$  $$\text{blue eyed boys =20/100}$$  $$\text{blue eyed girls =10/100}$$  $$ratio\,of\,girls\,to\,boys=3:4$$  $$hence$$  $$Blue\text{ eye boys=}\dfrac{1}{5}\times \dfrac{4}{7}=\dfrac{4}{35}$$  $$Blue\,eye\,girls=\dfrac{1}{10}\times \dfrac{3}{7}=\dfrac{3}{70}$$  $$Fraction\text{ of students having blue eyes=}\dfrac{4}{35}+\dfrac{3}{70}$$  $$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,=\dfrac{11}{70}$$ Mathematics

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