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#1 2007-02-21 17:44:50
- shivusuja
- Member
- Registered: 2006-09-14
- Posts: 56
progression
Find The 12th Term From Reverse Of An A.p
3,5,7,9
41
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#2 2007-02-21 20:33:38
- Jai Ganesh
- Administrator
- Registered: 2005-06-28
- Posts: 48,385
Re: progression
The nth term of an Arithmetic Progression (AP) is given by the formula
where tn is the nth term, a the first term and d the common difference, that is the difference between any two successive terms.
The number of terms in the AP can be found using the formula
where l is the last term, and n the number of terms.
Thus it can be seen that there are 20 terms in the AP you have given.12th term from reverse is the same as 9th from the beginning.
Hence, the ninth term from the beginning or twelfth term from the end would be 3+(8)2=3+16=19.
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