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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
Rishab Soni
let 35 raw scores be x1,x2,x3,......,x34,x35 average of 35 raw scores is 18 then [ (x1)+(x2)+(x3)+..….....+(x34)+(x35) ] / 35=18 [ (x1)+(x2)+(x3)+..….....+(x34)+(x35) ]=35(18)=630 (x1)+(x2)+.....+(x17)+(x18)+(x19)+...…....(x34)+(x35)=630......(1) given average of first seventeen of them is 14 then [ (x1)+(x2)+(x3)+......+(x17) ] / 17 =14 [ (x1)+(x2)+(x3)+......+(x17) ]=14(17)=238....(2) given average of last seventeen is 20 then [ (x19)+...…....(x34)+(x35) ] / 17 = 20 [ (x19)+...…....(x34)+(x35) ]=20(17)=340..…..(3) from (1)st,(2)nd, and (3)rd equations we have to substitute the 2nd and 3rd equations values in 1st equation then 238+(x18)+(340)=630 (x18)+578=630 x(18)=630-578=52 therefore,the eighteenth raw score is 52