Final answer:
To find the number of blue marbles in Margaret's bag, we use the given ratio of green to blue marbles (9:5) and the total number of marbles (28). Solving the resulting equation, we find that there are 10 blue marbles in the bag.
Step-by-step explanation:
The question asked by the student is centered around the concept of ratios and how they can be used to determine the composition of a set when its total size is known. Since Margaret's bag contains a total of 28 marbles, and the ratio of green to blue marbles is given as 9:5, we can find the number of blue marbles by solving the ratio equation.
Let's denote the number of green marbles as 9x and the number of blue marbles as 5x. Since the total number of marbles is 28, we have:
9x + 5x = 28
By simplifying, we get:
14x = 28
Dividing each side by 14 gives us:
x = 2
The number of blue marbles can now be found by multiplying 5 times x, so:
5x = 5(2) = 10
Therefore, there are 10 blue marbles in Margaret's bag.