[Video] Q4: The scatterplot above shows data collected on the lengths and widths of iris setosa petals. a line of best fit for the data is also shown. based on the line of best fit, if the width of an iris setosa petal is 19 millimeters, what is the predicted length, in millimeters, of the petal?

Explanation for Question 4 From the Math (Calc) Section on the Official Sat Practice Test 8

So question number four, it gives us a graph, right? 2 And it's a graph of the width of a, of a flower, 3 right. A pedal versus the length of a pedal. 4 And so they're asking us if a pedal were 19 millimeters wide, 5 what would we expect the length to be? And the best thing we can 6 do to solve this equation is going to be, to use the line of 7 best fit, which they've given us up here. 8 Right? But you'll notice that if you look in the line of best fit, 9 you don't see w and you don't see L all you see is X 10 and Y. And so the first step is going to be, 11 we're replacing our X and Y with our length and our width values right 12 now, if we look at our width, it's on the X axis. 13 So wherever we see an X, we're actually talking about width. 14 W now, if we look at our Y axis, 15 it says length, right? So wherever we see a Y we're actually talking about 16 length, so we can rewrite our equation at the bottom here. 17 So that instead of having the Y, we have an L and instead 18 of having an X, we'll put a w now, 19 all that we have to do is plug-in 19 for our w because 20 the question is asking us, what would the length be? 21 What would lb if our width, 22 or w was 19 millimeters. 23 When we plug that in, we'll get that our length is 1.6, 24 seven times 19 plus 21.1. 25 And then we plug that into our calculator, and we get the answer of 26 C.