Explanation for Question 18 From the Math (Calc) Section on the Official Sat Practice Test 9
Question 18 reads if P percent of an adult's daily allowance of potassium 2 as provided by X servings of crunchy grain cereal per day, 3 which of the following expresses P in terms of acts. 4 Okay. So questions 18 to 20 refer to the following information, 5 this paragraph, and the key sentence for question 18 is this last 6 one. In addition, each serving of the cereal provides 180 milligrams 7 of potassium, which is 5% of the daily allowance for adults. 8 And we know that's relevant because the question specifically references the allowance in potassium. 9 Now thinking about key, he is in percent and 10 X is servings. So X times 11 5% is going to be equal to P. 12 And from that alone, we can choose bees are correct answer. 13 We know that we can leave it as five X rather than 0.5 X 14 or 0.05 to the power box or anything like that, 15 because P is also in percent. 16 So we don't need to convert it into its decimal equivalent. 17 And another thing to think about is just logically what's going on here. 18 Essentially, you would multiply 5% by however many servings. 19 You had to figure out what percentage of your daily 20 allowance of potassium you'd had. So for example, 21 if you'd had two servings, your P would be two times 22 five, so that'd be 10 on. 23 It just makes logical sense, C and D refer more to a kind of, 24 um, exponential growth. 25 And I could theoretically make sense, 26 but again, the units on that, aren't quite right, 27 because it's not referring to.