A certain three cylinder combination lock has 70 numbers on it. To open it you turn to a number on the first cylinder then to a second number on the second cylinder and then to a third number on the third cylinder and so on until three number lock combination has been affected. Repetition are allowed and any of the 70 numbers can be used at each step to form the combination A) how many different lock combinations are there? B) what is the probability of guessing a lock combination on the first try? A) 343000
B) The probability that the correct lock combination is guessed on the first try is:

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Ответ:

yair7

20.09.2021

Mathematics

Step-by-step explanation:

Let the number of non-fiction books be x .

Then the number of fiction books= $\frac{2}{5}x$

Since, there are 56 books in the school library.

Then, $\\\Rightarrow\frac{2}{5}x+x=56$

$\frac{2x+5x}{5}=56\\\Rightarrow\ \frac{7x}{5}=56\\\Rightarrow\ x=\frac{56\times5}{7}\\\Rightarrow\ x=40$

Hence, the number of non fiction books = 40

Therefore, the number of fiction books = $\frac{2}{5}40=16$

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