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JEE Main Math Class 11 Sequences and Series Part 2 Questions
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© examsnet.com
Question : 63
Total: 100
If the
10
th
term of an A.P. is
1
20
and its
20
th
term is
1
10
, then the sum of its first 200 terms is:
[Jan. 8, 2020 (II)]
50
50
1
4
100
100
1
2
Validate
Solution:
T
10
=
1
20
=
a
+
9
d
. . . (i)
T
20
=
1
10
=
a
+
19
d
. . . (ii)
Solving equations (i) and (ii), we get
a
=
1
200
,
d
=
1
200
⇒
S
200
=
200
2
[
2
200
+
199
200
]
=
201
2
=
100
1
2
© examsnet.com
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