Posted by Abdela on Thursday, February 16, 2012 at 6:54am.
The sum of the first 5 terms of an arthmetic sequence, is 30 and the sum of the next 4 terms is 69 .
Find the arthemetic progression?

Math sequence  Reiny, Thursday, February 16, 2012 at 8:43am
so the sum of the first 9 terms would be 99
sum(5) = 30 > (5/2)(2a + 4d) = 30
5(2a+4d) = 60
2a + 4d = 12
a + 2d = 6
sum(9) = 99 > (9/2)(2a + 8d) = 99
2a + 8d = 22
a + 4d = 11
subtract them
2d = 5
d = 5/2 or 2.5
then a = 1
the arithmetic sequence is
1 , 3.5, 6, 8.5 , ...

Math sequence  Abubakar1idr, Thursday, February 16, 2012 at 2:26pm
What is lhe sum of lhe first 12 terms of an A.p whose first term is 15 and common difference is 13.

Math sequence  piyush, Tuesday, November 8, 2016 at 11:12am
1038
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