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What is the perimeter of a rectangle with a length of 7 cm and a width of 3 cm?
- A. 21 cm
- B. 10 cm
- C. 14 cm
- D. 20 cm
Correct Answer: D
Rationale: To find the perimeter of a rectangle, you add the lengths of all its sides. In this case, the formula for the perimeter of a rectangle is 2*(length + width). Substituting the given values, we get: 2*(7 cm + 3 cm) = 2*(10 cm) = 20 cm. Therefore, the correct answer is 20 cm. Choice A (21 cm) is incorrect because it is the sum of the individual sides rather than the perimeter. Choice B (10 cm) is incorrect because it only represents one side of the rectangle. Choice C (14 cm) is incorrect as it is not the total perimeter of the rectangle.
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How is the number -4 classified?
- A. Real, rational, integer, whole, natural
- B. Real, rational, integer, natural
- C. Real, rational, integer
- D. Real, irrational
Correct Answer: C
Rationale: The number -4 is classified as a real number because it exists on the number line. It is also a rational number since it can be expressed as -4/1. Additionally, -4 is an integer because it is a whole number that can be positive, negative, or zero. However, -4 is not a whole number because whole numbers are non-negative integers starting from zero. Similarly, -4 is not a natural number since natural numbers are positive integers starting from one. Therefore, the correct classification for the number -4 is real, rational, and integer, making option C the correct answer.
If Mom's car drove 72 miles in 90 minutes, how fast did she drive in feet per second?
- A. 0.8 feet per second
- B. 48.9 feet per second
- C. 0.009 feet per second
- D. 70.4 feet per second
Correct Answer: D
Rationale: To convert miles per hour to feet per second, first convert time to hours: 90 minutes = 1.5 hours. Then, calculate the speed in miles per hour: 72 miles in 1.5 hours = 48 mph. Finally, convert mph to feet per second using the conversion factor 1 mph = 1.47 feet per second: 48 mph * 1.47 = 70.4 feet per second. Therefore, the correct answer is 70.4 feet per second. Choices A, B, and C are incorrect because they do not reflect the correct conversion from miles per hour to feet per second.
Which of the following is NOT a way to write 40 percent of N?
- A. 0.4N
- B. N/40
- C. 2/5 N
- D. 40N/100
Correct Answer: B
Rationale: The correct answer is B: N/40. To find 40% of N, you multiply N by 0.4, so 0.4N is the correct representation. Choice B, N/40, is incorrect because dividing N by 40 does not give you 40% of N. Choice C, 2/5 N, is equivalent to 40% of N since 2/5 is the same as 40% when simplified. Choice D, 40N/100, is also correct since 40% can be represented as 40/100, which simplifies to 0.4, making 40N/100 another valid way to write 40% of N.
Which number is larger, 0.5 or 1/3?
- A. 0.5
- B. 1/3
- C. They are equal
- D. Cannot be determined
Correct Answer: A
Rationale: To compare 0.5 and 1/3, we can convert 0.5 to a fraction, which is 1/2. When comparing 1/2 and 1/3, we find that 1/2 is greater than 1/3. Therefore, 0.5 is larger than 1/3. Choice B is incorrect as 1/3 is smaller. Choice C is incorrect as the numbers are not equal. Choice D is incorrect as a clear comparison can be made.
Jessica buys 10 cans of paint. Red paint costs $1 per can, and blue paint costs $2 per can. In total, she spends $16. How many red cans did she buy?
- A. 2
- B. 3
- C. 4
- D. 5
Correct Answer: C
Rationale: Let r be the number of red cans and b be the number of blue cans. The total cans equation is r + b = 10. The total cost equation is r + 2b = 16. By solving these equations simultaneously, we find r = 4. Therefore, Jessica bought 4 red cans. Choice A, 2 red cans, is incorrect because it does not satisfy the total cans or total cost condition. Choices B and D are also incorrect as they do not fulfill both conditions simultaneously.