Question

The sum of first 20 terms of an ap 1,21,41.... is_______​

Answer 1

Answer:

$a=1\\d=21-1=20\\n=20\\S=n/2 * (2a+(n-1)d)\\=10(2+380)\\=10*382\\=3820\\\\HENCE THE ANSWER IS 3820$

HENCE THE ANSWER IS 3820

Step-by-step explanation:

Answer 2

d= 20

next number is 61

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