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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


Sagot :

[tex]\\ \rm\longrightarrow 1+2\dots +20[/tex]

Use Summation formula

[tex]\\ \rm\longrightarrow S_n=\dfrac{n(n+1)}{2}[/tex]

[tex]\\ \rm\longrightarrow S_{20}=\dfrac{20(20+1)}{2}[/tex]

[tex]\\ \rm\longrightarrow S_{20}=\dfrac{20(21)}{2}[/tex]

[tex]\\ \rm\longrightarrow S_{20}=\dfrac{420}{2}[/tex]

[tex]\\ \rm\longrightarrow S_{20}=210[/tex]

the answer is 210 :)