Find the 16th term of the AP 8, 10, 12, __ if it has a total 60 terms and hence find the sum of its last 10 terms
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Solution :
Given A.P=8,10,12....
n=60
a=8
d=2
an=a+(n−1)d
a60=8+59×2
=126
Hence sum of the last 10 items is
d=−2,a=126,r=10
s=
n
2
[2a+(n−1)d]
S=
10
2
[2×126+(10−1)(−2)]
=5(252−18)
=1170
Hence the sum of last to terms =1170
Given A.P=8,10,12....
n=60
a=8
d=2
an=a+(n−1)d
a60=8+59×2
=126
Hence sum of the last 10 items is
d=−2,a=126,r=10
s=
n
2
[2a+(n−1)d]
S=
10
2
[2×126+(10−1)(−2)]
=5(252−18)
=1170
Hence the sum of last to terms =1170
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