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The ratio of the number of boys and girls who participated in an examination is $4:3.$ The total percentage of candidates who passed the examination is $80$ and the percentage of girls who passed the exam is $90.$ The percentage of boys who passed is _______.

  1. $55.50$
  2. $72.50$
  3. $80.50$
  4. $90.00$ 
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Migrated from GO Electrical 4 years ago by Arjun

3 Answers

Best answer
4 votes
4 votes
$\text{Percentage of passed students} = \frac{\text{Percentage of boys passed} \times \text{#boys}+ \text{Percentage of girls passed}\times\text{#girls}}{\text{Total number of students}}$

Taking total number of students as $x$ and from the given statements,

$80 =  \frac{\text{Percentage of boys passed} \times \frac{4}{4+3}x + 90 \times \frac{3}{4+3}x}{x}$

$\implies80 \times 7 = 4 \times \text{Percentage of boys passed} + 3 \times 90 $

$\implies  \text{Percentage of boys passed} = \frac{560-270}{4} = \frac{290}{4} = 72.5$

Correct Answer: B
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Let total candidates attempting the exam be $70$.

In these Boys:Girls are in ratio $4:3$

$\Rightarrow$ There are $40$ boys and $30$ girls.

$80$% of the total candidates passed the exam = $\frac{80}{100}*70$ = $56$

$90$% of the girls passed the exam = $\frac{90}{100}*30$ = $27$

So Number of boys who passed the exam

= total candidates who passed the exam – total girls who passed the exam

= $56-27$

=$29$

$\therefore$ Percentage of boys who passed the exam = $\frac{29}{40}*100$ = $72.50$

So Option B $72.50$ is the correct answer.
2 votes
2 votes
$\text{Let no of boys B  = 4k ,G = 3k and total students = 7k }$

$\text{total passed students} =  0.8 * 7k$

$\implies \text{0.9 * 3k + X * 4k } = \text{0.8 * 7k}$

$\implies X =  0.725$

$\therefore \text{pass percentage of boys }  X = 72.5$
Answer:

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