If the mean deviation about the median of the numbers a,2a,3a........,50a is 50. Then "modulus of a" equals ?? plz answer fast..

Numbers are a,2a,3a.............50a Hence the numbers are arranged in ascending orderNow total numbers = 50 Hence value of n is oddmedian = 25a+26a2=25.5 aDeviation of the number about the median is a-25.5a,2a-25.5a........50a-25.5aMean deviation about the median =i=150xi-M50 a-25.5a+2a-25.5a+........50a-25.5a50=5024.5a+23.5a+22.5a+.........0.5a+0.5a+...............23.5a+24.5a =25002(0.5a+1.5a+..........24.5a) =25002×2520.5a+24.5a =2500      (as  sum of an A.P is n2(1st term+last term))25 ×25 a=2500a =2500625=4

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