Jill has 21 red roses and 28 white roses. she wants to make arrangements of flowers that look exactly the same with the same number of red roses and the same number of white roses in each arrangement. What is the greatest number of arrangements can she make?

To make the same number of red and white roses in each arrangement, Jill needs to find the greatest common divisor (GCD) of 21 and 28.

The prime factorization of 21 is 3 x 7.
The prime factorization of 28 is 2 x 2 x 7.

The common factors are 7 and 1, but the greatest common divisor is 7 because it is the highest factor shared by both numbers.

Therefore, Jill can make arrangements in which each arrangement has 7 red roses and 7 white roses.

The greatest number of arrangements she can make is determined by dividing the total number of red roses (21) by the number of red roses in each arrangement (7):

21 red roses / 7 red roses per arrangement = <<21/7=3>>3 arrangements

The greatest number of arrangements Jill can make is 3. Answer: \boxed{3}.

That’s wrong the answers are…

A: 7
B: 10
C: 14
D: 28

Apologies for the mistake. Let's recalculate the answer.

The greatest common divisor of 21 and 28 is 7. This means that Jill can make arrangements with 7 red roses and 7 white roses.

To find the number of arrangements she can make, we need to divide the total number of red roses (21) by the number of red roses in each arrangement (7):

21 red roses / 7 red roses per arrangement = 3 arrangements

So the correct answer is A: 7 arrangements.