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UPSC NDA II 2010 Mathematics Paper

Directions (Q.No. 7-10): The frequency distribution of life of 90 TV tubes whose median life is 17 months is as follows:

Life of TV tubes (in months)	No. of TV tubes
$0-5$ $5-10$ $10-15$ $15-20$ $20-25$ $25-30$	$3$ $12$ $x$ $35$ $y$ $4$

Question : 7 of 120

Marks: +1, -0

Solution:

Clearly median class will

15-20

using formula

M_{o}=l+\frac{\frac{N}{2} - \text{c.f.}}{f} \times i

Also

54+x+y=90

x+y=36

. . . (1)

Again

17=15+\frac{45-15-x}{35} \times 5

\Rightarrow 2=\frac{30-x}{y}

\Rightarrow x=30-14=16

\Rightarrow y=20

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