It actually works. When you get 1680 you just have to divide it by 3! to account for different orders of choosing 3 groups out of 9 people. 1680/2/3=280.

Let's say we are choosing 3 groups: A, B, and C. It doesn't matter if we choose A first or B first, right? that is why we need to divide by 3!

could you post what the answer is, please?

This problem is a little more complicated than just simple anagram method because you are choosing 3 groups of elements each containing 3 elements and the order is not important. Look at it this way. If you had 3 elements to choose from (A,B,C) in how many ways could you arrange them? ABC, ACB, BAC,...

Got even better idea how to help you understand :-) see, you are saying: "If you choose 3 different letters to represent the 3 groups (A, B, C) and If you set up 9 different slots: 9 8 7 6 5 4 3 2 1 A A A B B B C C C " and then you give your solution (9!/3!*3!*3!). According to this approa...

Because the first problem is a permutation problem while the second is a combination problem. The order of visiting teachers is important to us because it will create differnet schedules, but which bird was chosen first, second and third is not important (it will not affect the report)

If the scale model of a cube sculpture if .5 cm per every 1 m of the real sculpture, what is the volume of the model, if the volume of the real sculpture is 64 m^3. This is a very easy problem but for some reason I can't get it to work if i convert .5 cm to meters. .5 cm = .005 m I know that becaus...

Hi

(1) x is the first integer, then the average of the first nine integers is (x + (x+8))/2=7. Thus, x = 3. (x+(x+10))/2 = (3+13)/2 = 8

(2) x is the first integer, then the average of the last nine integers is ((x +2)+ (x+10))/2=9. Thus, x = 3. (x+(x+10))/2 = (3+13)/2 = 8

The answer is D