Question

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

Answer 1

Answer:

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

Let number of boys = 4X and number of girls = 5X

According to the question

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

⇒ 28X = 6 ( 5X - 100 )

⇒ 28X = 30X - 600

⇒ 2X = 600

∴ X = 600/2 = 300

∴ Number of boys = 4X = 4 x 300 = 1200

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