Its probably under harder 2unit in extension 1 but here's the question! please help
1,3,6,10,15....are called triangular numbers
Use the formula for the sum of an arithmetic series to find the 30th triangular number.
HSC 2009
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Subjects 09 (10 units):
Extension 1 Mathematics
Extension 2 Mathematics
Biology
Chemistry
English (Standard)
B.Pharmacy @ USYD 2010
1, 3, 6,10,15,.......
New set of series you can make from top
1+2+3+4+5+6+......
true since 1+2 = T2 from original
1+2+3 = T3 from original
1+2+3+4 = T4 (" ")
so on....
a= 1 n=30 d= 1
s30= 30/2 (2x1+(30-1)x1)
= 15x31
= 465
lol kev, cya
Last edited by ghostman_on_3rd; 6 Apr 2009 at 1:03 PM.
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UAI: 83+
HSC subjects 2009
- Standard English
- Extension 1 Mathematics
- Business Studies
- Ancient History
- Earth & Environmental Science
Sorry, I know this was a post a LOOONNGG time ago but why is d=1? Though you did say you made a replica series with 1+2+3+4+5... but may I ask of how exactly you derived that? If anyone passing this knows, please reach out. I'm sorry if it's a intuitive question, I just don't get the reasoning behind it yet. Thanks!
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