How many four digit codes are possible if the first and last digits cannot be a zero?

9000

Step-by-step explanation:

Yes, 9000 is correct. In order to count four digit numbers not beginning with 0 with no repeating digits, proceed one digit at a time. There are 9 possibilities for the first digit. Since the second digit must be distinct, there are 10−1=9 possibilities.

5050

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b: |12 – x| ≤ 0.25

step-by-step explanation:      

let x be the possible lengths in inches, of the ribbons jaime cut.

we have been given that jaime is cutting strips of ribbon for a project. he tries to cut each piece to be 12 inches long, but sometimes he cuts it too long or too short by as much as 0.25 inch.  

we can represent this information in an inequality as:

by the definition of absolute value function we will get,

upon combining our inequalities we will get,

therefore, the inequality   describes all the possible lengths (x), in inches, of the ribbons jaime cut.

step-by-step explanation: