Question

The mean of 20 numbers is 18. If 3 is added to each of first 10 numbers what will be the new set mean of 20 numbers.

Answer 1

Answer

Step-by-step explanation:

$\frac{x1+x2+x3+........+x20}{20}=18\\x1+x2+x3+........+x20=20*18\\x1+x2+x3+........+x20=360\\given\:3\:is\:added\:to\:first\:ten\:numbers\\=>\frac{(x1+3)+(x2+3)+(x3+3)+...+(x10+3).....+x20}{20}=k\\\frac{x1+x2+x3+........+x20+3*10}{20}=k\\\frac{x1+x2+x3+........+x20+30}{20}=k\\\frac{360+30}{20}=k\\\frac{390}{20}=k\\Therefore\\k=19.5$

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