Question

Is the sum of the first 25terms of the arithmetic sequence is 11,21,31,...became 2020 why?​

Answer 1

Answer:

a=11,d=10,n=25.

Sn25={2a+(n-1)d}*n/2

= (22+24*10)*25/2

= 3275.

hence it is wrong

Step-by-step explanation:

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