Explanation for Question 17 From the Math (Calc) Section on the Official Sat Practice Test 6
Question 17 reads, which of the following expresses the riser height in terms of 2 tread depth. Okay. 3 So questions 17 to 19, 4 we have to use the following information. 5 So we have to look at this figure and we also have to read 6 this paragraph. So reading through it says, 7 when designing a stairway, an architect can use the riser tread formula two H 8 plus D is equal to 25, 9 where H is the riser height in inches and D is the tread depth 10 in inches. Okay. So we can actually stop reading right here for this question. 11 We have this equation and looking down at our answer 12 choices. We see that all we have to do to answer this question is 13 just rearrange this equation to get H on one side and D on the 14 other. So we have two H plus D is equal 15 to 25. Let's subtract two H from each side to get, 16 excuse me, let's attract D from each side to get to H on its 17 own. So we have two H is equal to 25 minus D. 18 Okay. To get H on its own, 19 let's divide both sides by two. So we have H is equal to one 20 half times 25 minus D. 21 And that's going to be answer choice B for this question.