Multiply: 54 45. Express the result in decimal form.

Correct Answer: D

Rationale: To multiply 54 by 45, you should multiply the two numbers together: 54 x 45 = 2430. The decimal point is placed after counting the total decimal places in the numbers being multiplied. As there are no decimal places in the numbers 54 and 45, the result is 2430, which is correctly expressed as 24.3 when considering the decimal point placement. Choice A (0.0243) and Choice B (0.243) are incorrect as they represent fractions of 2430. Choice C (2.43) is incorrect as it incorrectly places the decimal point one place before the actual result.

Correct Answer: B

Rationale: To convert Fahrenheit to Celsius, you can use the formula: °C = (°F - 32) x 5/9. Substituting the Fahrenheit temperature of 59 degrees into the formula: °C = (59 - 32) x 5/9 = 27 x 5/9 = 135/9 = 15. Therefore, the approximate temperature on the Celsius scale is 15°C. Choice A is incorrect as it represents a negative temperature which is not the case here. Choice C and D are also incorrect as they do not match the calculated conversion from Fahrenheit to Celsius.

Correct Answer: A

Rationale: The scale of 3:1 means that for every 3 centimeters in the drawing, it represents 1 centimeter in real life. If the length of the cicada in the drawing is 6 centimeters, in real life, it would be 6 x 3 = 18 centimeters long. Therefore, the actual length of the cicada in real life is 18 centimeters. Choice B, 6.3 centimeters, is incorrect because it does not account for the scale factor. Choices C and D, 4.6 centimeters and 4.2 centimeters respectively, are also incorrect as they do not consider the 3:1 scale used in the drawing.

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: D

Rationale: To divide 3 by 4, we perform the division operation: 3 · 4 = 0.75. The correct answer is 0.75 (D). Choices A, B, and C are incorrect because they do not result from dividing 3 by 4. Choice A (5.75) is the result of dividing 23 by 4, choice B (5.875) is the result of dividing 7 by 1.2, and choice C (6.25) is the result of multiplying 5 by 1.25.