Question 1184050
.
In a swimming club, the ratio of th number of girls to the number of boys was 5:3. 
After 3 girls and 5 boys joined the club, the ratio became 7:5. How many girls were there in the club at first?
~~~~~~~~~~~~~~~~


<pre>
5x girls and 3x boys initially.


After joining


    {{{(5x+3)/(3x+5)}}} = {{{7/5}}}.


To solve, cross multiply. Then simplify


    5*(5x+3) = 7*(3x+5)

    25x + 15 = 21x + 35

    25x - 21x = 35 - 15

       4x     =    20

        x     = 20/4 = 5.


<U>ANSWER</U>.  The number of girls initially was  5x = 5*5 = 25.
</pre>

Solved.