Correct Answer: C

Rationale: The least common denominator of two fractions is the least common multiple of both denominators. This is because the least common denominator is the smallest number that both denominators can divide into evenly, ensuring that both fractions can be expressed with a common denominator. Choice A is incorrect as the least common denominator is a multiple of both denominators, not a number that multiplies into both. Choice B is incorrect because the common denominator needs to be a multiple of both denominators, not just a number they can divide into evenly. Choice D is incorrect as the greatest common factor is not used to find the least common denominator, but rather the least common multiple.

Correct Answer: C

Rationale: The correct answer is C. A rational number can be a whole number, fraction, or decimal. A rational number is any number that can be expressed as a ratio of two integers (where the denominator is not zero), which includes whole numbers, fractions, and decimals. Choice A is incorrect because rational numbers are not limited to being whole numbers. Choice B is incorrect because a rational number can be a fraction, decimal, or whole number. Choice D is incorrect because rational numbers can definitely be decimals, as long as the decimal representation is either terminating or repeating.

Correct Answer: A

Rationale: A mile is bigger than a kilometer. The correct conversion factor is 1 mile = 1.609 km. This means that one mile is equivalent to approximately 1.609 kilometers. Choice B is incorrect because a mile is bigger than a kilometer, and the conversion is not 1 km = 1.609 miles. Choice C is incorrect as the conversion factor provided is inaccurate; 1 mile is not equal to 1.5 km. Choice D is incorrect as it states that a kilometer is bigger, which is not true according to the actual conversion factor.

Correct Answer: B

Rationale: ollow the order of operations (PEMDAS: Parentheses, Exponents, Multiplication and Division (from left to right), Addition and Subtraction (from left to right)): Multiply: 7 3 = 21, and 4 2 = 8 Perform addition and subtraction: 6 + 21 - 8 = 19 Thus, the simplified expression equals 19.

Correct Answer: A

Rationale: The correct formula to find the circumference of a circle is C = 2πr, where C represents the circumference and r is the radius of the circle. Choice B, Circumference = πr², represents the formula for the area of a circle rather than the circumference. Choice C, Circumference = 2r², is incorrect as it does not involve π in the formula. Choice D, Circumference = r²π, has the terms reversed compared to the correct formula; the formula should start with the constant (2) multiplied by π, followed by the radius.