Final answer:
Charlie can use cord lengths between 22.5 centimeters and 27.5 centimeters for her keychains, calculated by the absolute value inequality |x - 25| ≤ 2.5.
Step-by-step explanation:
Charlie can use cord lengths that are within 2.5 centimeters of the desired 25 centimeters. To find the range of cord lengths, we'll create an absolute value inequality. The inequality is |x - 25| ≤ 2.5, where x represents the actual cord length.
The inequality can be interpreted as the actual cord length, x, being no more than 2.5 centimeters away from 25 centimeters, either shorter or longer. Solving the inequality:
- x - 25 ≤ 2.5
- x ≤ 27.5
- -2.5 ≤ x - 25
- -2.5 + 25 ≤ x
- 22.5 ≤ x
Thus, Charlie can use cord lengths that are between 22.5 centimeters and 27.5 centimeters in length.