11. Find the middle term of A.P 6,13,20............216
12. The 6th term of an A.P is -10 and its 10th term is -26. Determine the 15th term of an A.P
13. The 8th term of an A.P is O prove that its 38th term is triple its 18th term.
14. The sum of three numbers in A.P is 21 and their product is 231 find the numbers.
15. Find the sum of 25th term of an AP which nth term is given by tr=(7-3n)
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a=6
d=7
Tn= a+ (n-1)d
216=6+(n-1)*7
n=31
total no. of terms=31
middle term=(31+1)/2
=16th
T16= a+(16-1)d
= 6+(15*7)
=111
therefore the middle term of the AP is 111 answer
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