LalaB wrote:

Here I cant get the answer to the question 2

I thought that 0.1 decrease is equal to 100 increase(at least visually). why 200?

OK, now that I have a diagram, it makes perfect sense and I am happy to help.

First of all, here is a blog article on "

trend lines", also as known as "

best fit lines" or, more, formally, "

least-square linear regression lines."

http://magoosh.com/gmat/2012/gmat-integ ... tterplots/On that diagram, let's start simple. The line moves to the right two "grids" for every one "grid" it goes down. In other words, it moves to the right one "grid" for every half "grid" it goes down. So we could say that the slope is

slope = - (one vertical grid)/(two horizontal grids)

Now, what do these grids mean? The vertical axis is measured in hours to fatigue, and each grid, from one horizontal gray line to the next, is 0.2 hours, so half the distance between two adjacent horizontal gray lines is 0.1 hour. That's what Question #2 wants, a 0.1 hour decrease in time to fatigue. Well, in the space it takes for the line to drop half the distance between two adjacent horizontal gray lines, it goes the full distance between two vertical gray lines. The horizontal scale is area, measured in (cm)^2. Notice that the distance between two adjacent vertical gray lines is 200 (cm)^2. That's why, if we cross the entire distance between two adjacent vertical gray lines while dropping half the distance between two adjacent horizontal gray lines, we go down 0.1 hrs vertically and go up 200 (cm)^2 horizontally.

Does all this make sense?

Mike

_________________

Mike McGarry

Magoosh Test Prep

Education is not the filling of a pail, but the lighting of a fire. — William Butler Yeats (1865 – 1939)