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. $23/49$

Answer 1

The correct option is A $11/70$

$\text{Let total number of students be 100}$
$\text{blue eyed boys =20/100}$
$\text{blue eyed girls =10/100}$
$ratioofgirlstoboys=3:4$
$hence$
$Blue\text{eye boys=}\frac{1}{5}\times \frac{4}{7}=\frac{4}{35}$
$Blueeyegirls=\frac{1}{10}\times \frac{3}{7}=\frac{3}{70}$
$Fraction\text{of students having blue eyes=}\frac{4}{35}+\frac{3}{70}$
$=\frac{11}{70}$