Correct Answer: Option A
প্রথমত,
a1 + (n - 1)*d= an [n = মোট সংখ্যা]
[d = পরপর দুইটি সংখ্যার পার্থক্য = 4 - 1 = 3]
অর্থাৎ,
1 + (n - 1)*3 = 73
or, (n - 1)*3 = 73 - 1
or, (n - 1) = 72/3
or, n = 24 +1 = 25
এখন,
সমষ্টি, Sn= n*(a1 + an)/2
= 25* (1 + 73)/2
= 925
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