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Math is Fun, arithmetic sequence
The Sum Of 11 Term Of An A.P Is 891.Find The 28 Term And 45 Term.The Common Is 15.
2 answers
d = 15
sum from k = 0 to n-1 of (a + k d) = (n/2)[ 2 a + (n-1)d ]
n = 11
d = 15
891 = (11/2) [ 2 a + 150 ]
891 = 11 a + 825
11 a = 66
a = 6
now
Tn = 6 + (n-1) 15 so finish
sum from k = 0 to n-1 of (a + k d) = (n/2)[ 2 a + (n-1)d ]
n = 11
d = 15
891 = (11/2) [ 2 a + 150 ]
891 = 11 a + 825
11 a = 66
a = 6
now
Tn = 6 + (n-1) 15 so finish
1 answer