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A bag contains books numbered 1 to 20 . Three books are drawn from the bag with replacement. The probability that largest number on the book is 7 .
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Verified Answer
The correct answer is:
$\left(\frac{7}{20}\right)^3-\left(\frac{6}{20}\right)^3$
The total probability of selecting 3 books and whose page number is less than or equal to 7 is $\left(\frac{7}{20}\right)^3$.
Total probability of selecting 3 books whose page number is less than 7 is $\left(\frac{6}{20}\right)^3$.
$\therefore$ Requiried probability $=\left(\frac{7}{20}\right)^3-\left(\frac{6}{20}\right)^3$
Hence, option (4) is correct.
Total probability of selecting 3 books whose page number is less than 7 is $\left(\frac{6}{20}\right)^3$.
$\therefore$ Requiried probability $=\left(\frac{7}{20}\right)^3-\left(\frac{6}{20}\right)^3$
Hence, option (4) is correct.
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