A few days ago
Jenny V.

i need help with these two precalc questions?

i don’t want the answers, i just need help fiquring out how to get the answers.

1.) A security code has seven characters. Each code begins with two digits, then two letters, and finally three difits. The number of distinct securtiy codes possible if repetition is allowed it…

2.) How many ten-digit phone numbers are possible if a number may not begin with a 0 or a 1?

Top 1 Answers
A few days ago
Anonymous

Favorite Answer

1.

There are 10 possibilities for each of the first two characters, giving 10^2. Similarly for each of the next two characters there are 26^2 possibilities (if only one case is used). 3 digits at the end are treated in the same way. Multiply all the results together (as they are independent) to get the total number of codes.

2.

There are 8 possiblities for the first digit, and then 10 for each of the 9 remaining digits. Use the same technique as in question 1.

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