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Question

The product of which of the following is a rational number?

The correct answer is √27 × √3

Finding the Rational Number Product

The question asks us to identify which product among the given options results in a rational number. A rational number is any number that can be expressed as the quotient or fraction $\frac{p}{q}$ of two integers, where $p$ is an integer and $q$ is a non-zero integer. Examples include 1, 0, -5, $\frac{1}{2}$, $0.75$. An irrational number, on the other hand, cannot be expressed this way, like $\sqrt{2}$ or $\pi$. We are looking for the option that gives a Rational Number Product.

Analyzing Products of Square Roots

We need to evaluate each product of square roots provided in the options to determine if the result is a rational number or an irrational number. We can use the property of square roots that $\sqrt{a} \times \sqrt{b} = \sqrt{a \times b}$.

Option 1: $\sqrt{2} \times \sqrt{3}$

Let's calculate the product:

$\sqrt{2} \times \sqrt{3} = \sqrt{2 \times 3} = \sqrt{6}$

The number 6 is not a perfect square (it's not the square of an integer). Therefore, $\sqrt{6}$ is an irrational number. This is not the Rational Number Product we are looking for.

Option 2: $\sqrt{9} \times \sqrt{5}$

Let's calculate the product. We can simplify $\sqrt{9}$ first or multiply directly:

Method 1: Simplifying Radicals first:

$\sqrt{9} \times \sqrt{5} = 3 \times \sqrt{5} = 3\sqrt{5}$

Since $\sqrt{5}$ is an irrational number (5 is not a perfect square), the product $3\sqrt{5}$ is also an irrational number.

Method 2: Multiplying Square Roots first:

$\sqrt{9} \times \sqrt{5} = \sqrt{9 \times 5} = \sqrt{45}$

To see if $\sqrt{45}$ is rational, we can try Simplifying Radicals by finding perfect square factors of 45. $45 = 9 \times 5$.

$\sqrt{45} = \sqrt{9 \times 5} = \sqrt{9} \times \sqrt{5} = 3\sqrt{5}$

Again, we find the result is $3\sqrt{5}$, which is an irrational number. This is not the desired Rational Number Product.

Option 3: $\sqrt{27} \times \sqrt{3}$

Let's calculate this product of Square Roots:

$\sqrt{27} \times \sqrt{3} = \sqrt{27 \times 3} = \sqrt{81}$

Now, we need to check if 81 is a perfect square. We know that $9 \times 9 = 81$.

$\sqrt{81} = 9$

The number 9 is an integer. An integer can be expressed as a fraction, for example, $9 = \frac{9}{1}$. Therefore, 9 is a rational number. This product results in a Rational Number Product.

Option 4: None of these

Since we found that the product in Option 3 is a rational number, this option is incorrect.

Conclusion on the Rational Number Product

By evaluating each option, we found that the product $\sqrt{27} \times \sqrt{3}$ results in the number 9, which is a rational number. The other products involved an Irrational Number. Thus, the product $\sqrt{27} \times \sqrt{3}$ is the Rational Number Product among the given choices.

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Important Questions from Rational or Irrational Numbers

  1. Which of the following number is irrational?

  2. Which of the following numbers will have an irrational square root?

  3. What is the square root of 16 + 6√7?

  4. A non-terminating but recurring decimal is:

  5. Which of the following is false?

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