Subtract and simplify: -5 - (-6) =

Correct Answer: C

Rationale: To simplify the expression -5 - (-6), we can rewrite it as -5 + 6 (since subtracting a negative number is equivalent to adding its positive counterpart). This gives us -5 + 6 = 1. Therefore, the correct answer is 1. Choice A, ½, is incorrect because the subtraction of a negative number results in a positive number. Choices B and D are also incorrect as they do not match the simplified result of -5 - (-6), which is 1.

Correct Answer: A

Rationale: To determine the initial amount she had, we subtract the amount spent ($18) from the total amount she had after spending. If she had $1,070 after spending, subtracting $18 gives us $1,052, which was the initial amount. Choices B, C, and D are incorrect as they do not consider the subtraction of the amount spent to find the initial amount.

Correct Answer: C

Rationale: To convert pounds to kilograms, you need to divide the weight in pounds by the conversion factor of 2.2 (1kg = 2.2lbs). 180 pounds / 2.2 = 81.82 kg Rounded to the nearest whole number, the weight of 180 pounds is approximately 82kg. Therefore, the correct answer is 82kg, which is option C. Option B (75kg) is not correct as it is significantly lower than the calculated value. Options A (68kg) and D (90kg) are also incorrect as they do not match the converted weight of 180 pounds.

Correct Answer: B

Rationale: The total number of marbles in the bag is 5 (red) + 7 (blue) = 12 marbles. The probability of drawing a red marble is the number of red marbles divided by the total number of marbles: 5/12. Simplifying 5/12 gives 1/3. Therefore, the correct probability of drawing a red marble is 1/3. Choice A (1/4) is incorrect because there are more red marbles than 1/4 of the total marbles. Choice C (1/2) is incorrect as it represents half of the total marbles. Choice D (2/3) is incorrect as it implies there are more red marbles than there actually are.

Correct Answer: B

Rationale: Rationale: 1. Let x be the volume of the 10% solution needed and y be the volume of water needed. 2. The total volume of the final solution is 200ml, so x + y = 200. 3. The concentration of the final solution is 5%, so the amount of salt in the final solution is 0.05 * 200 = 10g. 4. The amount of salt in the 10% solution is 0.1x, and the amount of salt in the water is 0, so the total amount of salt in the final solution is 0.1x. 5. Since the total amount of salt in the final solution is 10g, we have 0.1x = 10. 6. Solving for x, we get x = 100ml. 7. Substituting x =