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# Adam forgot his 4-digit pin code. He knows it consists of three 5's and one 7. How big of a chance is there...

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Adam forgot his 4-digit pin code. He knows it consists of three 5's and one 7. How big of a chance is there that he types the correct code in one try?

Feb 27, 2019

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Adam forgot his 4-digit pin code. He knows it consists of three 5's and one 7.

How big of a chance is there that he types the correct code in one try?

$$\begin{array}{|r|c|} \hline \text{code}& \text{chance of correct code} \\ \hline 5557 & 25\ \% \\ \hline 5575 & 25\ \% \\ \hline 5755 & 25\ \% \\ \hline 7555 & 25\ \% \\ \hline \end{array}$$

Feb 27, 2019
#2
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For these types of questions, I like to use a drawn-out graph. Since there are four possible digits, you should have four rows, each for one digit

and since you have all four out of four digits id draw four rows again, creating a chart. fill that out, and you'll see that there are four possibilities

If you only knew three digits, then you would have to add many more rows. I hope this helps

 5 5 7 5 7 5 5 5 5 7 5 5 5 5 5 7

Sorry the graph was too big

BTW: this is my first answer in the forums!!! Glad to be a part of the community

-DBZ

Feb 27, 2019