If the sum of 1st and 20th term of an arithmetic sequence is 60, what is the 4th term
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1
Answer:
Given,
a
1
+a
20
=88
a.
a
2
+a
19
=(a
1
+d)+(a
20
−d)
=a
1
+a
20
=88
b.
a
10
+a
11
=a
1
+9d+a
20
−9d
42+a
11
=a
1
+a
20
∴a
11
=88−42=46
c.
d=a
11
−a
10
=46−42=4
d.
a
10
=a+9d
a=42−9(4)
∴a=6
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