Question

in a school the ratio of the number of the boys to the number of girls 4:5 when 100 girls leave the school the ratio becomes 6:7 find the number of boys in the schook​

Answer 1

Answer:

There are 1,200 boys in school. Step-by-step explanation:

Let,

The number of the boys in a school = 4x

The number of the girls in a school = 5x

When 100 girls leave the school

The number of the girls in a school = 5x - 100

Also,

The ratio becomes 6 : 7

So,

$\sf{\dfrac{4x}{5x \: - \: 100} \: = \: \dfrac{6}{7}}$

⇒ 7 (4x) = 6 (5x -100)

⇒ 28x = 30x - 600

⇒ 28x - 30x = - 600

⇒ - 2x = - 600

⇒ 2x = 600

⇒ x = 600 / 2

⇒ x = 300

___________________

The number of the boys in a school = 4x

⇒ 4 (300)

⇒ 1200

Therefore, there are 1,200 boys in school.

Answer 2

Question:-

• In a school the ratio of the number of the boys to the number of girls 4:5 when 100 girls leave the school the ratio becomes 6:7 find the number of boys in the school.

To Find:-

• Find the number of boys.

Solution:-

• Let the number of boys in school be 4x

• Number of girls be 5x

According to the Question:-

$\sf\longrightarrow \: \dfrac { 4x } { 5x - 100 } = \dfrac { 6 } { 7 }$

$\sf\longrightarrow \: 7 \times 4x = 6( 5x - 100 )$

$\sf\longrightarrow \: 28x = 30x - 600$

$\sf\longrightarrow \: 30x - 28x = 600$

$\sf\longrightarrow \: 2x = 600$

$\sf\longrightarrow \: x = \cancel\dfrac { 600 } { 2 }$

$\sf\longrightarrow \: x = 300$

Hence ,

• Number of boys area 4x = 1200