Question

find the sum of the first 1000 positive integer

Answer 1

no. of terms 'n'=1000

first term 'a'=1

last term 'an'=1000
therefore,
Sn=n/2(a+an)

Sn=1000/2(1+1000)

Sn=500(1001)

Sn=500500

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Answer 2

Answer:

$\huge{\pink{\boxed{\green{\sf{S_{1000}=500500}}}}}$

Step-by-step explanation:

$\huge{\pink{\boxed{\green{\underline{\red{\sf{[SOLUTION-]}}}}}}}$

☆ Let S = 1+2+3+4+5................+1000

${ \orange{to \: find}} \\ { \pink{ \boxed{ \green{ s_{1000} = }}}}$

☆ According to given question:

$\to s_{n} = \frac{n}{2} (a + l) \\\to s_{1000} = \frac{1000}{2}(1 + 1000) \\ \to s_{1000} = 500 \times 1001 \\ { \pink{ \boxed{ \green{\therefore s_{1000} = 500500}}}}$

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