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## anonymous 4 years ago To use a school copier, a 4- digit code using the digits 0-9 must be entered. If each code cannot begin with the number 0 and there are 81 acceptable codes, what is the probability that someone will randomly select a usable code?

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1. anonymous

$$\frac{1}{81}$$??

2. anonymous

how many four digit numbers are there?

3. anonymous

does not say

4. anonymous

number acceptable ---------------- will be the answer total number

5. anonymous

sure it does... use four digits, 0 to 9.... how many possible codes are there?

6. anonymous

i got one

7. anonymous

let's see... 0000 0001 0002 0003 0004 ... 9999 so there are how many possible codes?

8. anonymous

when u divide

9. anonymous

81/10,000

10. anonymous

that looks right to me

11. anonymous

probability questions usually boil down to number of good ways / number of all the ways

12. anonymous

thank you

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