You are here:

# Advanced Math/In and out rules

Question
What is the rule for this table?
X= 3,6,9
Y= 5, 10, 15
I cant figure it out for my sons 3rd grade math!

If you graph the data points (3, 5), (6, 10), and (9, 15), you can draw a straight line through them.
The rule for the table is the equation of that line.

Use two of the points to calculate the slope of the line.
rise = 15 - 10 = 5
run = 9 - 6 = 3
slope = rise/run = 5/3

Use the slope and one of the points (say, (6, 10)) to determine the equation of the line.
y - 10 = (5/3)(x - 6)
This equation is in "point-slope" form. However,  "slope-intercept" form is more convenient for filling in a data table.

Convert the equation to slope-intercept form:
y = (5/3)x

Volunteer

#### Janet Yang

##### Expertise

I can answer questions in Algebra, Basic Math, Calculus, Differential Equations, Geometry, Number Theory, and Word Problems. I would not feel comfortable answering questions in Probability and Statistics or Topology because I have not studied these in depth.

##### Experience

I tutor students (fifth through twelfth grades) and am a Top Contributor on Yahoo!Answers with over 24,000 math solutions.

Publications
Co-author of An Outline of Scientific Writing: For Researchers With English as a Foreign Language

Education/Credentials
I have a Bachelor's degree in Applied Mathematics from the University of California at Berkeley.

Past/Present Clients
George White Elementary School. Homework Help program at the Ridgewood Public Library, Ridgewood, NJ. Individual students.