According to the Closure Property, which of these sums results in a rational number?

A. square root 36 + square root 221
B. pi + square root 4
C. 0.6 + 9/10
D. 0.6479953469975... + 3/4

1 answer

The Closure Property states that a set is closed under an operation if performing that operation on members of the set always produces a member of the same set. In this case, we are considering sums that yield rational numbers.

Let's evaluate each option:

A. \(\sqrt{36} + \sqrt{221}\)

  • \(\sqrt{36} = 6\) (which is rational)
  • \(\sqrt{221}\) is irrational.
  • Therefore, \(6 + \sqrt{221}\) results in an irrational number.

B. \(\pi + \sqrt{4}\)

  • \(\sqrt{4} = 2\) (which is rational)
  • \(\pi\) is irrational.
  • Therefore, \(\pi + 2\) results in an irrational number.

C. \(0.6 + \frac{9}{10}\)

  • \(0.6\) is equivalent to \(\frac{6}{10}\) or \(\frac{3}{5}\) (which is rational).
  • \(\frac{9}{10}\) is also rational.
  • Therefore, \(0.6 + \frac{9}{10} = \frac{6}{10} + \frac{9}{10} = \frac{15}{10} = 1.5\), which is rational.

D. \(0.6479953469975... + \frac{3}{4}\)

  • \(0.6479953469975...\) is a decimal number that does not terminate or repeat exactly. It is not a rational number (infinite non-repeating decimal).
  • \(\frac{3}{4}\) is rational.
  • Therefore, the sum \(0.6479953469975... + \frac{3}{4}\) is likely to also be irrational.

Thus, the only sum that results in a rational number is option C: 0.6 + 9/10.