Question

You are an avid coin collector. You decide to start keeping better track of your coin collection. After 15 days you count and find out you have 155 coins. After 22 days you have a total of 218 coins. Write an equation in slope intercept form to represent this situation.

Answer 1

y = 9x + 20

Explanation:

It's given that after 15 days there were 155 coins and after 22 days there were 218 coins.

If we plot the ordered pairs in terms of number of days and number of coins,

Let the equation of the line is,

y - y' = m(x - x')

where m = slope of the line

And (x', y') is a point lying on the line

Ordered pairs will be, (15, 155) and (22, 218).

Slope of a line passing through two points
`(x_1,y_1)` and
`(x_2,y_2)` is given by,

Slope 'm' =
`(y_2-y_1)/(x_2-x_1)`

m =
`(218-155)/(22-15)` = 9

Equation of the line passing through (15, 155) and slope = 9 will be,

y - 155 = 9(x - 15)

y - 155 = 9x - 135

y = 9x + 20