Correct Answer: A

Rationale: To find the length of the unknown leg (a) of a right triangle, use the Pythagorean theorem: a² + 9² = 19². Substitute the known values, solve for a: a² + 81 = 361. Subtract 81 from both sides to get a² = 280. Taking the square root of 280 gives a ≈ 16.7 feet. Therefore, the correct answer is 16.7 feet. Choice B (16.0 feet) is incorrect as it does not accurately round to the nearest tenth. Choice C (17.4 feet) and choice D (8.4 feet) are incorrect as they do not match the calculated value using the Pythagorean theorem.

Correct Answer: A

Rationale: The equation D=2R means that D equals 2 times R, which translates to D being twice the value of R. Therefore, choice A, 'D is twice as much as R,' is the correct representation of the relationship between D and R. Choice B, 'R is twice as much as D,' incorrectly reverses the roles of D and R. Choice C, 'R is two times D,' incorrectly states the relationship between R and D. Choice D, 'D is two more than R,' does not accurately reflect the relationship presented in the equation.

Correct Answer: B

Rationale: The correct way to find the factors of a number is to identify all pairs of numbers that, when multiplied together, result in the given number. This method allows you to determine all the factors of the number. Choice A is incorrect because dividing the number by all possible numbers is not an efficient way to find its factors. Choice C is incorrect as listing all the multiples of the number does not give the factors. Choice D is unrelated to finding factors as adding the digits of a number together does not provide information about its factors.

Correct Answer: B

Rationale: To find 31% of 426, multiply 0.31 by 426. This gives 0.31 426 = 132.06. Therefore, choice B, 132.06, is the correct answer. Choice A, 425.69, is close to the original number but is not the correct answer for the percentage calculation. Choice C, 13.7, is not the correct result for 31% of 426. Choice D, 0.07, is significantly lower than the correct answer and does not represent 31% of 426.

Correct Answer: C

Rationale: In the number 0.08573, the digits are positioned after the decimal point as follows: 0.08573. The correct answer is '5 in the second decimal place' because 5 is the second digit after the decimal point. Choice A is incorrect as there is no '0' after the decimal point. Choice B is incorrect as '8' is the first digit after the decimal point. Choice D is incorrect as '3' is the fourth digit after the decimal point.