Explanation for Question 13 From the Math (No Calc) Section on the 2018 May Sat
Question 13 says the equation P equals 14.7 plus 2 0.4, three 90 approximates, 3 the pressure P in pounds per square inch exerted on a diver at a 4 depth of D feet below the surface of the water. 5 What is the increase in depth that is necessary to increase the pressure by 6 one pound per square inch. So to solve this, 7 I'm just going to set an arbitrary value for P um, 8 we're going to solve for D and then we're going to see how much 9 D would increase if we increased our arbitrary amount for P by one. 10 So let's start by setting P or the pressure equal to 14 point 17. 11 When we do that, the 14 point 17 cancels out in both sides and 12 we just get zero is equal to 0.4, 13 390 or D is equal to zero. 14 So let's see how D changes when we increase the pressure. 15 By one, if we set the pressure to 15.7 plus 16 0.439 D, 17 then instead we have one is equal to 0.3 90 or 18 one over 0.4, 19 three nine is equal to D. 20 So when we increase the pressure by one, 21 the depth increases by one over 0.439. 22 So the correct answer here is a.