To determine whether the sum of \( \sqrt{25} \) (which is 5 and definitely a rational number) and 18 (also a rational number) is rational or irrational, we can apply the properties of rational and irrational numbers.
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Identify the types of numbers:
- \( \sqrt{25} = 5 \) is a rational number.
- 18 is also a rational number.
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Closure property of rational numbers: The sum of two rational numbers is always a rational number.
Given that both \( 5 \) (from \( \sqrt{25} \)) and \( 18 \) are rational, their sum \( 5 + 18 = 23 \) is also rational.
Thus, the correct response is: Rational, because both addends are rational.