Find the sum of all natural number from 20 to 30
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21+22+23+24+25+26+27+28+29=225
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natural no. from 20—21, 22, 23, 24, 25, 26, 27, 28, 29—30
a¹=21, d=a²-a¹
a²=22, d=22-21 = 1
sum of all =Sn= S¹¹ ,n=11
Sn= n/2[2a¹+(n-1)d]
S¹¹=11/2[2×21+(11-1)1]
=11/2[42+(10)1]
=11/2(42+10)
=11/2×52
=572/2
S¹¹=286
Sum of all natural from 20 to 30= 286
PLZ DON'T FORGET TO MAKE AS BRAINLIEST
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