Explanation for Question 15 From the Math (Calc) Section on the Official Sat Practice Test 6
Question 15 gives us this table of X and Y values. 2 And it asks us which of the following equations relates Y to X for 3 the values in the table above. Now I think that the easiest way to 4 solve for this one is not necessarily by trying to plot X and Y 5 or do anything crazy to find the relationship yourself. 6 I think the easiest way would just be to plug in these X values 7 one by one and see if they get you the corresponding Y value. 8 And if they do, then you know that you've got the right answer choice. 9 So let's look at answer choice. A first we've got one half times 10 five over two to the power of X. 11 So it's in X is equal to one. And that gets us to 1.25, 12 which is the same thing in fraction form as five, 13 over four. So already we can cross out a because when you plug in 14 X equals one in this expression, we do not get the Y value that 15 we need, which is 11 over four. So let's move on to two or 16 let's move on to B, excuse me. We have, 17 Y is equal to two times three fourths to the X. 18 And again, let's plug an ax as equal to one. We got that. 19 Our answer is 1.5, 20 which infraction form is three over two. 21 And again, we can cross it out because we're looking for Y to be 22 equal to 11 over four. 23 Next for the linear expressions we've got, Y is equal to three-fourths X plus 24 two. So plugging in again, 25 X is equal to one. We have three fourths times one plus two is 26 equal to 2.75, which is equivalent to 11 over four. 27 Okay. So it seems lik...