You can lower the price by 20% if you buy more than fifteen units of iPhone cases. If you pay $500 to buy 18 units, what is the original price? Give the rationale and then the answer.
Let's think step by step. If you buy 18 units, the percentage of the total price drops to 100% - 20% = 80%. If 80% is equal to $500, then 100% is equals 100% / 80% * $500 = $625.. The answer is: 625.

James is trying to avoid eating too much sodium. He's making a recipe that calls for 2 teaspoons of salt and 8 oz of parmesan cheese. Salt has 50 mg of sodium per teaspoon and parmesan has 25 mg of sodium per oz. If he can't reduce the salt, how many fewer ounces of parmesan cheese does he need to use to reduce the total amount of sodium by 1/3rd? Give the rationale and then the answer.
Let's think step by step. First find how much sodium the parmesan has in total by multiply the amount of sodium per ounce by the number of oz: 25 mg / oz * 8 oz = 200 mg. Then use the same process to find how much sodium is in the salt: 50 mg / tsp * 2 tsp = 100 mg. Then find the total sodium in the recipe by adding the sodium from the cheese and the salt: 100 mg + 200 mg = 300 mg. Then multiply the total amount of sodium by 1 / 3 to find how much less sodium James wants: 300 mg * 1 / 3 = 100 mg. Then divide this amount by the amount of sodium per ounce of cheese to find how many fewer ounces of cheese he needs: 100 mg / 25 mg / oz = 4 oz.. The answer is: 4.

Every day, Bob logs 10 hours of work in his office. If he works for five days a week, calculate the total number of hours he logs in a month. Give the rationale and then the answer.
Let's think step by step. In a week, working 10 hours a day, Bob logs 10 * 5 = 50 hours. After a month with 4 weeks, Bob logs 4 * 50 = 200 hours for his office working hours.. The answer is: 200.