Question 599207
Hi, there--
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number of ways to write first digit (0-9) = 10
number of ways to write second digit (0-9) = 10
number of ways to write the first letter (upper- or lowercase) = 52
number of ways to write the second letter (upper- or lowercase)  = 52
number of ways to write the third letter (upper- or lowercase)  = 52
number of ways to write the fourth letter (upper- or lowercase)  = 52
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In combinatorics, the fundamental principle of counting, states that if we have A ways of doing something and B ways of doing another thing, then there are A*B ways of performing both actions. So, we multiply the six numbers together:
{{{10*10*52*52*52*52=10^2+52^4=100*7311616=7311616}}}
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There are 7,311,616 ways to create a password for the internet site.
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Hoope this helps. Feel free to email me via gmail if you have questions about the solution.
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Ms.Figgy
math.in.the.vortex@gmail.com