An Arithmetic series has 20 terms. The first term is - 81. The sum of all the terms is - 480. Use the arithmetic sum formula to find the last term

Question

Mathematics

Teresa Manning

27 June, 18:33

An Arithmetic series has 20 terms. The first term is - 81. The sum of all the terms is - 480. Use the arithmetic sum formula to find the last term

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Answers (1)

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Jimmy Sawyer · Answer 1

The last term is 33.

Step-by-step explanation:

Sn = (n/2) (a1 + L) where a1 = first term and L = the last.

So:

-480 = (20/2) (-81 + L)

-480 = 10 (L - 81)

L - 81 = - 480 / 10 = - 48

L = - 48 + 81

L = 33.