Question

the ratio of number of boys to that of girls in a group becomes 2 : 1 when 15 girls leave .but, afterwards when 45 boys also leave,the ratio become 1:5.originally the number of girls in the group was ​

Answer 1

didnt u derstand the question properly

Answer 2

Number of girls in the class is 40

Step-by-step explanation:

Let the number of boys are x and number of girls are y

When 15 girls leave ratio of boys and girls become 2:1

So $\frac{x}{y-15}=\frac{2}{1}$

$x=2y-30$------eqn 1

Now in second case when 45 boys leave then ratio become 1:5

So $\frac{x-45}{y-15}=\frac{1}{5}$

$5x-225=y-15$

$5x-y=210$---eqn 2

Multiplying equation 1 by 5

$5x=10y-150$

Solving equation 1 and 2

$210-y=10y-150$

$9y=360$

y = 40 girls

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