Question

In a school, the ratio of boys and girls is 4:5. When 100 girls leave the school, the ratio becomes 6:7. How many boys are there in the school?

• A. 1800
• B. 1200
• C. 1000
• D. 1500

Answer 1

Answer:

B. 1200

Solution:

Ratio of Boys to Girls is 4 : 5

Let us take Number of Boys = 4x and Number of girls = 5x

when 100 girls Leave the School,

the ratio become 6 : 7

Which means.,

$\frac{4x}{5x-100}=\frac{6}{7}$

$4x\times{7}=6\times{(5x-100)}$

$28x=30x-600$

$30x-28x=600$

$2x=600$

$x=300$

Number of Boys in the School $= 4x=4\times{300}=1200$