Question

in our school the ratio of boys to girls is 4 :5 when 1000 girls leave the school the ratio changes to 6:7how many boys are there in the school​

Answer 1

let x = the multiplier

then

4x = original number of boys

and

5x = original number of girls

4x/(5x-100) =6 /7

Cross multiply

7(4x) = 6(5x-100)

28x = 30x - 600

600 = 30x - 28x

600 = 2x

x = 600/2

x = 300 is the multiplier

then

4(300) = 1200 boys

Answer 2

☞ In a school the ratio of boys to girls is 4:5. When 1000 girls leave the school the ratio changes to 6:7. How many boys are there in the school?

Solution:

Let number of boys be B

And number of girls be G.

» Boys : Girls = 4 : 5 ____ [GIVEN]

If 1000 girls leave the school the ratio becomes 6 : 7.

• A.T.Q.

$\dfrac{4x}{5x \: - \: 1000}$ = $\dfrac{6}{7}$

Cross-multiply them

=> 7(4x) = 6(5x - 1000)

=> 28x = 30x - 6000

=> 28x - 30x = - 6000

=> - 2x = - 6000

=> x = 3000

______________________________

Number of Boys = 4x = 4(3000)

= 12000

______________[ANSWER]