अनुक्रम \(2,6,12,20,\ldots\) में (100) से छोटे कितने पद हैं?
In the sequence \(2,6,12,20,\ldots\), how many terms are less than (100)?
Explanation opens after your attempt
A. (9)
Concept
Here (a_n=n(n+1)), and \(9\times10=90\) while \(10\times11=110\). So (9) terms are less than (100).
Why this answer is correct
The correct answer is A. (9). Here (a_n=n(n+1)), and \(9\times10=90\) while \(10\times11=110\). So (9) terms are less than (100).
Exam Tip
यहाँ (a_n=n(n+1)) है और \(9\times10=90\) जबकि \(10\times11=110\) है। इसलिए (9) पद (100) से छोटे हैं।
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