Question

The coorrdinate grids show the cost of different numbers of bookmarks .How many cents do 4 bookmarks cost?

Answer 1

54 cents

Explanation:

The cost of bookmarks relating to the number of bookmarks is shown in the coordinate grid. x represents the number of bookmarks and y represents the cost of each bookmark in cents.

The equation of a line passing through the points
`(x_1,y_1)\ and\ (x_2,y_2)` is given by:

`y-y_1=(y_2-y_1)/(x_2-x_1)(x-x_1)`

From the coordinate grid, it has the points (2, 30) and (7, 90). Therefore, the equation is:

`y-30=(90-30)/(7-2)(x-2)\\\\y-30=12(x-2)\\\\y-30=12x-24\\\\y=12x+6`

Therefore the cost of 4 bookmarks (x = 4):

y = 12(4) + 6

y = 48 + 6

y = 54 cents