Correct Answer: C

Rationale: If a horse can trot around a track twice in 10 minutes, it completes one circle in 5 minutes. To determine how many times it will circle the track in half an hour (30 minutes), divide the total time by the time taken for one circle: 30 minutes / 5 minutes per circle = 6 times. Therefore, the horse will circle the track 6 times at the same speed in half an hour. Choice A, 3 times, is incorrect as it does not consider the correct time taken for a single circle. Choice B, 5 times, is incorrect as it miscalculates the total number of circles within half an hour. Choice D, 10 times, is incorrect as it overestimates the number of circles the horse can complete in the given time frame.

Correct Answer: C

Rationale: If Jolene bikes 5 miles for every 30 minutes, it means she bikes 10 miles in one hour (twice the 30-minute interval). Therefore, in 2 hours, she will cover double the distance she bikes in one hour, which equals 20 miles (10 miles per hour x 2 hours = 20 miles). This makes Choice C, '20 miles,' the correct answer. Choices A, B, and D are incorrect as they do not account for the correct doubling of the hourly distance when calculating the total distance biked in 2 hours.

Correct Answer: B

Rationale: The Hindu-Arabic numeral system consists of ten digits: 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. These ten digits are used as the fundamental symbols to represent numbers in this numerical system. Choice A, 'Two,' is incorrect as there are more than two digits in the system. Choice C, 'Twelve,' is incorrect as it exceeds the total number of digits in the system. Choice D, 'Twenty,' is incorrect as it overestimates the number of digits present in the Hindu-Arabic numeral system.

Correct Answer: C

Rationale: When dividing 2,032 by 25, you find that 25 goes into 2,032 a total of 81 times without exceeding it. The remainder is 7, not 28 as stated in choice B. This is because 25 * 81 = 2,025, leaving a difference of 7, not 28. Choice A and D are incorrect because they do not correctly represent the division result of 2,032 by 25.

Correct Answer: B

Rationale: The scale of 1:30 means that 1 inch on the plan represents 30 inches in actual size. If the width of the barn door on the plan is 3 inches, the actual width is calculated by multiplying 3 inches by the scale factor (30), giving 90 inches. To convert inches to feet, divide by 12 (since 12 inches = 1 foot), resulting in 90 inches · 12 = 7.5 feet. Therefore, the correct answer is 10 feet (option B), not 7.5 feet. Option A (90 inches) is the result before converting to feet, option C (9 feet) is the incorrect conversion if the initial calculation was done correctly, and option D (7.5 feet) is the incorrect conversion of the initial calculation.