There are 40 boys in 6th grade. The number of girls in 6th grade is 30. Carly says that means the ratio of the number of boys in 6th grade to the number of girls in 6th grade is 4:7. Is Carly correct? If not, what is the correct answer?

Best answer that i found on yahoo ok   set :   x= length of 2nd piece in cm  x- 3= length of 1st piece in cm  x-4= length of 3rd piece in cm  then since you know they all came from the 20 cm ribbon you add them together and set them equal to 20x+ x-3 +x-4 = 20  3x - 7= 20  3x= 27  x= 9  the shortest piece is the third piece which is x- 4  x-4  9-4 = 5  the length of the smallest piece is 5 cm.  the other lengths are  9 cm  6 cm