Explanation for Question 6 From the Math (No Calc) Section on the 2019 May Sat
Question six says blood volume, 2 VB in a human can be determined using the equation. 3 VB equals VP over one minus age where VP is the plasma 4 volume and age is the hematocrit, 5 the fraction of blood volume that is red blood cells, 6 which of the following correctly expresses the hermatocrit in terms of the blood volume 7 and the plasma volume. So with these types of questions, 8 the paragraph is a little bit wordy, but all you really need to know 9 is what is the original equation. 10 So in this case, that's right here. 11 And what are able, are you trying to get on the left side of 12 the equation, which is right here, 13 H and you can also see that by looking at all the answer choices, 14 all of them have H on the left side. So I'm going to rewrite 15 this original equation. BB equals VP over one 16 minus H. 17 So now all we need to do is reorder these variables to get H 18 on the left side. So let's start by multiplying both sides by one minus 19 age that gives us Phoebe times one minus H equals B 20 P. Then we're going to divide both sides by VB. 21 We get one minus age is equal to VP over VB. 22 And then I'm going to add H to the other side and subtract VP 23 over VB. And that gives me one minus V P over 24 VB, physical to H. 25 And that is answer choice a so a is the correct answer.