Question

Ben has $5. In order to have money for a new tablet computer, Ben is going to sell his collection of stamps for $3 per stamp. Ben has decided to graph a line showing the relationship between the number of stamps he sells and the total amount of money he has. Which will be the y-intercept of Ben's graph?

Answer 1

5

Explanation:

It is 5 because no matter how many stamps he sells, he has $5.

Answer 2

The y-intercept of Ben's graph is
`y = 5`.

Explanation:

The function for Ben's amount of money y, depending on the number of stamps sold x, is as follows:

`y = ax + b`

In which a is the price of each stamp and b is his initial money.

Building the function:

Ben has $5. This means that if he sells no stamps, he is still going to have $5. So
`b = 5`.

For each stamp sold, he gains $3. So if sells 1 stamp, he will have $8, if he sells 2, he will have $11. So
`a = 3`.

The function is:

`y = 3x + 5`

Which will be the y-intercept of Ben's graph?

This is the value of y when x = 0.

So

`y = 3*0 + 5 = 5`

The y-intercept of Ben's graph is
`y = 5`.