evaluate the following expression x y xy if x 4 and y 2
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HESI A2

HESI A2 Math Practice Exam

1. Evaluate the following expression: -x + y + xy, when x = 4 and y = 2.

Correct answer: B

Rationale: To evaluate the expression, substitute x = 4 and y = 2 into the expression: -4 + 2 + 4*2. Calculate each term: -4 + 2 = -2, then 4*2 = 8. Adding these results gives -2 + 8 = 6. Therefore, the correct answer is 6. Choice A (2) is incorrect as it does not consider all terms in the expression. Choice C (12) is incorrect as it miscalculates the result by failing to account for the negative sign. Choice D (8) is incorrect as it doesn't consider the negative value of the first term in the expression.

2. If a car's gas tank is 3/4 full and the tank holds 16 gallons when full, how many gallons are in the tank?

Correct answer: A

Rationale: To find out how many gallons are in the tank when it is 3/4 full, you need to calculate 3/4 of 16 gallons. 3/4 of 16 is (3/4) x 16 = 12 gallons. Therefore, the car's gas tank contains 12 gallons when it is 3/4 full. Choice B (8 gallons) is incorrect because that would be 1/2 of the tank's capacity, not 3/4. Choice C (14 gallons) is incorrect as it exceeds the full capacity of the tank. Choice D (10 gallons) is incorrect as it is less than 3/4 of the tank's capacity.

3. Convert to metric: 7 grams = x milligrams

Correct answer: C

Rationale: To convert grams to milligrams, you need to multiply by 1,000 since there are 1,000 milligrams in a gram. Therefore, 7 grams is equal to 7,000 milligrams. Choice A (700 mg) is incorrect because it represents grams to milligrams incorrectly. Choice B (0.7 mg) is incorrect as it converts grams to milligrams erroneously by decimal placement. Choice D (0.07) is incorrect as it converts grams to milligrams inaccurately by misplacing the decimal point.

4. Donna has 4.2 liters of fertilizer. If each pecan tree needs 0.7 liters of fertilizer and Donna uses all the fertilizer, how many pecan trees does Donna have?

Correct answer: A

Rationale: To find the number of trees, divide the total amount of fertilizer (4.2 liters) by the amount needed for each tree (0.7 liters). 4.2 / 0.7 = 6 trees. Therefore, Donna has 6 pecan trees. Choice A is correct because the calculation is done accurately. Choices B, C, and D are incorrect as they do not reflect the correct calculation based on the given information.

5. What is 25% of 400?

Correct answer: D

Rationale: To find 25% of a number, multiply the number by 0.25 (since 25% is the same as 25/100 or 0.25). In this case, 400 x 0.25 = 100. Therefore, 25% of 400 equals 100. Choice A, 800, is incorrect because it is the result of multiplying 400 by 2, not by 0.25. Choice B, 10,000, is also incorrect as it is significantly higher than the correct answer. Choice C, 200, is incorrect as it is the result of dividing 400 by 2, not by 0.25.

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