Solution
A1
= 41, n=30, An = 107, S30 =?
Sn
= n(A1 + An)
2
S30
= 30(41 + 107)
2
S30
= 15 x 148
S30
= 2220
Hence the sum of all 20 terms is 1480.
TRYTHIS………………….
The first term
of an AP is 15 and the last term is 113. If the arithmetic progression consists
of 30 terms, calculate the sum of all the terms.
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