Respuesta :

sqdancefan

Answer:

  400

Step-by-step explanation:

The 20 terms of the sum can be formed into 10 pairs, each with a sum of 40:

  = (1 +39) +(3 +37) +(5 +35) + ... +(19 +21)

  = 40 × 10 = 400

The indicated sum is 400.

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