## Lachlan1996 Group Title Help with mathematical combinations please. Points A, B, C, D, E, F, G, H, and I are arranged in two rows such that we have A - B - C - D - E and F - G - H - I How many triangles can be formed having vertices chosen from these points? How many of these triangles have the point A as one of their vertices? one year ago one year ago

1. Lachlan1996 Group Title

Sorry it is A - B - C - D - E F - G - H - I

2. Lachlan1996 Group Title

Awesome thank you for visiting unklerhaukus!!!

3. UnkleRhaukus Group Title

|dw:1360476356312:dw|

4. Lachlan1996 Group Title

Yes they are to act as the vertices of triangles.

5. UnkleRhaukus Group Title

so either two points are from the top line (and one from the bottom line) or one point is from the top line (and two from the bottem line)

6. Lachlan1996 Group Title

Hmm i see, let me try that, i wasnt sure how to interpret it.

7. UnkleRhaukus Group Title

because if all three points were on the same line , you couldn't make a triangle

8. Lachlan1996 Group Title

Yes that appears to work, 5C1 x 4C2 and 5C2 x 4C1 which adds to 70

9. Lachlan1996 Group Title

Though can I ask how you determine how to do these questions? I havent really got a problem solving type of mind, so i find it difficult to think laterally.

10. UnkleRhaukus Group Title

$^nC_k = \frac{n!}{k!(n-k)!}$

11. Lachlan1996 Group Title

No i understand the general formula of the combination theory. I just often have difficulty understanding how I am meant to approach the question, what guidelines I need to follow.

12. Lachlan1996 Group Title

Once you had explained those guidelines i knew exactly what to do, i just dont know how to determine the parameters to follow.

13. UnkleRhaukus Group Title

i like to start with a picture usually

14. Lachlan1996 Group Title

Are there any other tricks you can use to figure out whats going on? or is it just trying to pull apart the question, and making assumptions to rules.

15. UnkleRhaukus Group Title

im not sure how to answer that,

16. Lachlan1996 Group Title

Ah well, im sure i'll just have to pick it up as I go. You've helped enough already. Thank you very much for the assistance. I wish you a good afternoon. Thank you for the help mate, I appreciate the effort :) Have a good one mate, and stay well!

17. UnkleRhaukus Group Title

sometimes rewriting the question into a simpler form can help