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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: 45,956

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.


It appears to me that if one wants to make progress in mathematics, one should study the masters and not the pupils. - Niels Henrik Abel.

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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