Find the sum of first 20 terms of the arithmetic progression 3, 8, 13, ..
using the formula.
Answers
Answered by
2
Answer:
In this problem,
a
=
3
,
r
=
8
−
3
=
5
,
n
=
20
and
s
20
=
?
.
We will use the formula
s
n
=
n
2
(
2
a
+
(
n
−
1
)
d
)
s
20
=
20
2
(
2
(
3
)
+
(
20
−
1
)
5
)
s
20
=
10
(
6
+
95
)
s
20
=
10
(
101
)
s
20
=
1010
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