PART - 2 CH - 8 Sequences and Series — Maths STD 11 Science — Question
CBSE BoardEnglish MediumSTD 11 ScienceMathsPART - 2 CH - 8 Sequences and Series1 Mark
Question
Find the sum of odd numbers from 1 to 2001.
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Answer
To find the number of terms in $1+3+5+\ldots \ldots$. 2001, \[ \begin{aligned} a_n & =a+(n-1) d \\ 2001 & =1+(n-1) \times 2 \\ \Rightarrow \quad \frac{2000}{2} & =(n-1) \Rightarrow n=1001 \end{aligned} \] We know that sum of $n$ odd numbers is $n^2$. $\therefore$ Sum of 1001 odd numbers $=(1001)^2$
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