makingachange2 makingachange2
  • 22-01-2022
  • Mathematics
contestada

Determine the sum of the first 20 terms of an arithmetic sequence in which first
terms is 31 and the twentieth term is 109

Respuesta :

sqdancefan
sqdancefan sqdancefan
  • 22-01-2022

Answer:

  1400

Step-by-step explanation:

The average term is the average of the first and last terms.

  average term = (31 +109)/2 = 70

The sum of the 20 term is 20 times the value of the average term:

  S20 = 20(70) = 1400

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