Correct Answer: B

Rationale: The correct answer is B: 1. The average width of a doorway typically ranges from 0.8 to 1.2 meters, making 1 meter a reasonable estimate. Choice A (0.5) is too narrow for a standard doorway. Choice C (10) is too wide for a typical doorway. Choice D (3) is also wider than the standard width of a doorway.

Correct Answer: B

Rationale: To find the sale price after a 15% discount, you calculate 15% of $78, which is $11.70. Subtracting $11.70 from the original price gives $66.30. Since the price is typically rounded, the estimated sale price is $66. Choice A, $12, is too low and does not reflect a 15% discount off $78. Choice C, $22, and choice D, $69, are also incorrect as they do not accurately estimate the sale price after a 15% discount.

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: To find the force needed to stretch the coil 0.1 meters, we can set up a proportion based on the given information. The initial force and stretch are in direct proportion, so we can use this relationship to determine the unknown force. (132 N / 0.07 m) = X / 0.1 m. Cross-multiplying, we get 132 N * 0.1 m / 0.07 m = 188.57 N, which rounds to 188.6 N. Therefore, the correct answer is 188.6 Newtons. Choice A is incorrect as it does not match the calculated answer. Choice B is significantly higher and does not align with the proportional relationship. Choice D is close but does not account for the correct rounding as specified in the question.