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What number is 20 equal to 40% of?
- A. 50
- B. 8
- C. 200
- D. 5000
Correct Answer: A
Rationale: To find the number that 20 is equal to 40% of, you can set up the equation: 20 = 0.4 * x, where x is the unknown number. To solve for x, divide both sides of the equation by 0.4. This gives x = 20 / 0.4 = 50. Therefore, 20 is 40% of 50.
Choice B, 8, is incorrect because 20 is not equal to 40% of 8. Choice C, 200, is incorrect because 20 is not equal to 40% of 200. Choice D, 5000, is incorrect because 20 is not equal to 40% of 5000. The correct answer is 50.
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A scientist is trying to determine how much poison will kill a rat the fastest. Which of the following statements is an example of an appropriate hypothesis?
- A. Rats that are given lots of poison seem to die quickly.
- B. Does the amount of poison affect how quickly the rat dies?
- C. The more poison a rat is given, the quicker it will die.
- D. Poison is fatal to rats.
Correct Answer: C
Rationale: A valid hypothesis must be a testable statement that predicts a relationship between variables. Option C is the only statement that presents a clear cause-and-effect relationship between the amount of poison given and the time it takes for the rat to die. Option A is descriptive without predicting an outcome, option B is a question rather than a statement, and option D is a general fact about poison and rats, lacking a specific hypothesis for testing.
If 5y - 7 = 13, what is y?
- A. 4
- B. 5
- C. 6
- D. 7
Correct Answer: A
Rationale: To solve the equation 5y - 7 = 13, start by adding 7 to both sides to isolate the term with y: 5y = 20. Then, divide by 5 to solve for y, which gives y = 4. Therefore, the correct answer is A. Choice B, C, and D are incorrect as they do not yield the correct solution when substituted into the equation. It's important to follow the proper steps in solving linear equations to arrive at the correct answer.
Shawna buys 5 gallons of paint. If she uses 2/5 of it on the first day, how much paint does she have left?
- A. 3 gallons
- B. 2 gallons
- C. 1 gallon
- D. 0.5 gallons
Correct Answer: A
Rationale: To find out how much paint Shawna uses on the first day, calculate 2/5 * 5 = 2 gallons. Subtracting the amount used from the total amount gives us 5 - 2 = 3 gallons remaining. Therefore, Shawna has 3 gallons of paint left after using 2 gallons on the first day. Choice A is correct. Choices B, C, and D are incorrect because she has more paint left than the options presented.
Four people split a bill. The first person pays for 1/3, the second person pays for 1/4, and the third person pays for 1/6. What fraction of the bill does the fourth person pay?
- A. 1/4
- B. 1/6
- C. 1/3
- D. 1/12
Correct Answer: D
Rationale: To find out what fraction of the bill the fourth person pays, you first calculate the total fraction paid by the first three people: 1/3 + 1/4 + 1/6 = 4/12 + 3/12 + 2/12 = 9/12 = 3/4. This means that the first three people paid 3/4 of the bill. Therefore, the fourth person pays the remaining fraction: 1 - 3/4 = 1/4. So, the fourth person pays 1/4 of the bill. Choice A, 1/4, is incorrect because this is the total fraction paid by the first person. Choice B, 1/6, is incorrect as this is the fraction paid by the second person. Choice C, 1/3, is incorrect as this is the fraction paid by the third person.
Express 18/5 as a reduced mixed number.
- A. 3 3/5
- B. 3 1/15
- C. 3 1/18
- D. 3 1/54
Correct Answer: A
Rationale: 18/5 = 3 with a remainder of 3, so it is 3 3/5.
3 1/15 is equivalent to 46/15 which is greater than 18/5
3 1/18 converts to 55/18 which is also greater than 18/5
3 1/54 converts to 163/54