Question 223632
This  is  basically  an  arithmetic  series 1,2,3,,,24
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form  is  a(n) = a(1) +(n-1)d,,,,,where  d  is  difference  btwn  terms, and  n = 3 terms
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a(24) = 1+(24-1)1 = 24
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The  sum  of  an  arithmetic  series  is,,S= n{ a(1) +a(n)} /2
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S= 24(1+24)/2 = 300
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check,,,use  calc  to  manually  add  series,,,300,,,,ok