Explanation for Question 20 From the Math (No Calc) Section on the Official Sat Practice Test 9
Question 20 gives us this graph and it asks us the graph of the 2 linear function F is shown in the X, 3 Y plane above the graph of the linear function. 4 G not shown is perpendicular to the graph of F and passes through the 5 0.13. What is the value of G of zero? 6 Okay. So essentially we've got this line right here, 7 this function F and we're trying to find something out about a different linear 8 function G so breaking down this problem 9 into parts, the first thing to recognize is that G is perpendicular to 10 the graph of F perpendicular means that the slope is the 11 opposite reciprocal. So let's first find the slope of this 12 F function, and then we can figure out the slope of the linear function. 13 G so one approach to find the slope is we 14 can use the method of two points. 15 So we have zero three and we have one, 16 one. 17 So Y two minus Y one over X, 18 two minus X, one to cause a negative two over one. 19 So have a slope of negative two. And you also could find that out 20 just by doing the simple rise over run formula. 21 We've got the rise being negative two and the run being one. 22 So that's a slope of negative two. Now, 23 knowing the slope of F is equal to negative two, 24 and that the slope of G is perpendicular or that the line of G 25 is perpendicular. We know that the slope of G is going to be equal 26 to one half, 27 because again, it's a flip sign and it's the reciprocal. 28 We also know that the linear function G passes through 0.13. 29 So let's...