The common difference of an ap is -2 find its sum of first term is hundred and last term is -10 with full solution
1 answer:
Answer:
2520
Step-by-step explanation:
The n th term of an AP is
= a₁ + (n - 1)d
where a₁ is the first term and d the common difference.
To find the number of terms given = - 10 , d = - 2 and a₁ = 100, then
100 - 2(n - 1) = - 10 ( subtract 100 from both sides )
- 2(n - 1) = - 110 ( divide both sides by - 2 )
n - 1 = 55 ( add 1 to both sides )
n = 56 ← number of terms
Given n, a₁ and a₅₆ , then the sun of the terms is
=
(a₁ + a₅₆ )
= (100 - 10) = 28 × 90 = 2520
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