Question

1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+19+20= A)0 B)210 C)220 D)Brainliest

Answer 1

The answer is 210 :)

Answer 2

$\\ \rm\longrightarrow 1+2\dots +20$

Use Summation formula

$\\ \rm\longrightarrow S_n=\dfrac{n(n+1)}{2}$

$\\ \rm\longrightarrow S_{20}=\dfrac{20(20+1)}{2}$

$\\ \rm\longrightarrow S_{20}=\dfrac{20(21)}{2}$

$\\ \rm\longrightarrow S_{20}=\dfrac{420}{2}$

$\\ \rm\longrightarrow S_{20}=210$