To solve this problem, we need to determine the range of guesses that would be considered correct in the contest. The actual number of beans in the jar is given as 645. To win, the guess must be within 20 beans of the actual number.
This can be expressed with the equation:
∣ x − 645∣ ≤ 20
This equation expresses that the difference between the guess x and the actual number 645 should be 20 or less.
This inequality can be rewritten as:
− 20 ≤ x − 645 ≤ 20
By adding 645 to all parts of the inequality, we find:
625 ≤ x ≤ 665
Therefore, the minimum number of beans that could be guessed correctly is 625, and the maximum number is 665.
Hence, the correct equation that represents this scenario is:
∣ x − 645∣ = 20 ; maximum guess: 665 beans
So, the maximum guess that could still win the contest is 665 beans.