Can someone plz help me with my math homework?
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Hi… I know it’s late, so the chances of someone who can help me being online are slim, but I can try…
I’m doing math homework… algebra… and in the problem, there are figures, pyrimads of circles (figure one has one dot (circle), figure 4 has four dots along each side, 5 has 5 dots on each side, and so on. They all sort of look like equilateral triangles. theres a chart with the fig. number and the number of dots in each figure:
Fig: 1 2 3 4 5 6
# dots: 1 3 6 10 15 21
and so on. We’re supposed to come up with a formula (sentence, statement, etc…) that tells you how many dots are in ANY figure, without knowing the number of dots in the figure before it. plz help me!!!!!!! oh, I am punkrocker7362 on aim if you can talk to me that way, it’s easier than emailing back and forth… I’m online now.
Hi… I know it’s late, so the chances of someone who can help me being online are slim, but I can try…
I’m doing math homework… algebra… and in the problem, there are figures, pyrimads of circles (figure one has one dot (circle), figure 4 has four dots along each side, 5 has 5 dots on each side, and so on. They all sort of look like equilateral triangles. theres a chart with the fig. number and the number of dots in each figure:
Fig: 1 2 3 4 5 6
# dots: 1 3 6 10 15 21
and so on. We’re supposed to come up with a formula (sentence, statement, etc…) that tells you how many dots are in ANY figure, without knowing the number of dots in the figure before it. plz help me!!!!!!! oh, I am punkrocker7362 on aim if you can talk to me that way, it’s easier than emailing back and forth… I’m online now. I know that it sounds really complicated… but it’s not that hard, it’s just hard to explain w/o the pictures…
February 5th, 2009 at 1:44 pm
That’s easy.
Just use the forumula for traingle numbers.
n(n+1), all divided by 2.
February 7th, 2009 at 9:35 pm
well I don’t really understand what it’s supposed to look like, but the # of dots is like +2, +3, +4… and so on.
It’s an arithmetic series.
Sn = (n/2) (2a1 + (n-1)d)
Sn = the # dots you’re trying to find.
n = the figure number you’re trying to find the # dots for.
a1 = the # dots for figure 1, which is 1.
d= difference, which is +1
So, for figure 6:
Sn = (6/2) (2 + (6-1)1)
Sn = (3)(7)
Sn = 21
Since that proves that it works, you can try something like, figure 134:
Sn = (134/2) (21 + (134-1)1)
Sn = (67) (154)
Sn = 10,318 dots
I hope that was easy to understand, and I hope that’s what you were looking for.