The sum of the first 11 terms of an arithmetic sequence is 220.
a) Find the 6^ =n term.
b) Find the sum of the 5^ prime h and 7^ \# terms.
c) Find the sum of the 1 ^ 51 and the 11^ iff terms.
Answers
SOLUTION
CORRECT QUESTION
The sum of the first 11 terms of an arithmetic sequence is 220.
a) Find the 6th term.
b) Find the sum of the 5th and 7th term
c) Find the sum of the 1st and the 11th term
FORMULA TO BE IMPLEMENTED
If in an arithmetic progression
First term = a
Common difference = d
1. nth term of the AP = a + ( n - 1 )d
2. Sum of first n terms of an arithmetic progression
EVALUATION
Let First term = a and Common difference = d
Here it is given that sum of the first 11 terms is 220
Thus we have
a) The 6th term of the AP
b) 5th term of the AP
= a + ( 5 - 1)d
= a + 4d
7th term of the AP
= a + ( 7 - 1)d
= a + 6d
Hence the required sum
= a + 4d + a + 6d
= 2a + 10d
c) 1st term = a
11th term of the AP
= a + ( 11 - 1)d
= a + 10d
Hence the required sum
= a + a + 10d
= 2a + 10d
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