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Mathematics

The mean of 5 variables is 20. If four of them are 15, 25, 10 and 12; the fifth variable is :

  1. 38

  2. 60

  3. 48

  4. 28

Statistics

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Answer

Let fifth variable be x.

By formula,

Mean = Sum of observationsNo. of observations\dfrac{\text{Sum of observations}}{\text{No. of observations}}

∴20=15+25+10+12+x5⇒20×5=x+62⇒100=x+62⇒x=100−62=38.\therefore 20 = \dfrac{15 + 25 + 10 + 12 + x}{5} \\[1em] \Rightarrow 20 \times 5 = x + 62 \\[1em] \Rightarrow 100 = x + 62 \\[1em] \Rightarrow x = 100 - 62 = 38.

Hence, Option 1 is the correct option.

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