Number of boys in the gym class = 12 Number of girls in the gym class = 10 then Ratio of boys to ratio of girls = 12:10 = 6:5 Now Number of boys joining the gym class later = 6 So after the new boys join the number of boys in the gym class becomes = 18 The ratio of boys to girls have to remain the same Let us assume that the number of girls that need to join the gym class = x Then 6/5 = 18/(x + 10) 6(x + 10) = 18 * 5 6x + 60 = 90 6x = 90 - 60 6x = 30 x = 30/6 = 5 So the number of girls that need to join the gym class to keep the ratio same is 5. I hope the procedure is clear enough for you to understand.
So 12 and 10 if 6 boys joined then it is now 12+6=18 so we now need to have 12:10=18:x solve for x convert to fraction 12/10=18/x multiply both sides by x 12x/10=18 multiply both sides by 10 12x=180 divide both sides by 12 x=15 so from 10 to 15 is a difference of 5 so 5 girls need to join
