in arithmetic progression an = a1 + (n-1)d s = n (a1 + an)/2 in this question, a1 = 10 d = - 1/3 an will be an= 10 -1/3 (n-1) s= n (10 + 10 - 1/3 (n-1)) / 2 = 155 n (20 - 1/3 n + 1/3) = 310 20 n - 1/3 n2 + 1/3 n = 310 60 n - n2 + n = 930 n2 - 61 n + 930 = 0 (n - 30) (n -31) = 0 n = 30 or n = 31

CA Foundation doubt

false

Explain question 9..

Asked by Arpita27 Jun 2024307 views

4 answers

Arpita · 27 Jun 2024
Thnk you 😊
Aaryan · 27 Jun 2024
in arithmetic progression an = a1 + (n-1)d s = n (a1 + an)/2 in this question, a1 = 10 d = - 1/3 an will be an= 10 -1/3 (n-1) s= n (10 + 10 - 1/3 (n-1)) / 2 = 155 n (20 - 1/3 n + 1/3) = 310 20 n - 1/3 n2 + 1/3 n = 310 60 n - n2 + n = 930 n2 - 61 n + 930 = 0 (n - 30) (n -31) = 0 n = 30 or n = 31
Arpita · 27 Jun 2024
How
Aditya · 27 Jun 2024
Answer will be both a and b

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