Question

A long-distance company charges 45 cents per minute or fraction of a minute for each call. Which graph models this situation?

Answer 1

A step (or staircase) function.

These functions are constant in given intervals, and non continuous between one interval and the other.

Assume that the x axis represents the time, in minutes, and the y axis represents the cost in dollars.

The interval
`[0,1]` counts as fraction of a minute or one minute, so the cost is 0.45.

The interval
`(1,2]` counts as fraction of two minutes or two minutes, so the cost is 0.90.

In general, the interval
`(n-1, n]` counts as fraction of
`n` minutes or
`n` minutes, so the cost is
`n\cdot 0.45`

Answer 2

The answer is A, the first graph