Greatest Integer Function

Building a
Step Function

Domestic Rates
Data

   ATT True Reach Savings
   MCI Basic Residential
   LCI All America Plan

Modeling Phone Data

Phone companies will determine the price of a call by rounding the length of the call to a certain time period (either one minute or six seconds). For instance, a local weekday call on MCI's Basic Residential plan will cost $0.2599 each minute.

How much would a 5.2 minute call cost?

Solution

Questions

Answer the following questions using the Domestic Rates Data locations shown to the left. Round each answer to TWO DECIMAL PLACES. SHOW YOUR WORK on a separate sheet of paper. Press TAB after answering each question on the screen.

1. What is the cost of a 10.2 minute, evening, 38 mile call on ATTs True Reach Savings? ANSWER = $

2. Find the price for this month's phone bill that contains one 28.4 minute, 208 mile, Sunday evening call on MCIs Basic Residential plan. Don't forget the national service fee! ANSWER = $

3. Find the ceiling function that will determine the price of a phone bill containing one Sunday evening call on MCIs Basic Residential plan. Let t represent the length of the phone call. Graph the function and verify your answer to question 2 using one of the following methods (depending on your technology):

Java Function Grapher from Cognologic Software: Click on the icon to the left. Let x(t)=t, set the window from t = 25 to t = 30, DO NOT check aspect ratio, and use ceil(t) to represent the ceiling function in y(t).
Note: The function will not appear discrete due to a small bug in the program.
Graphing calculator
Geometer's SketchPad file: Click on the compass icon to the left. (Directions for Dowload).
YOUR INPUT TO THE RIGHT SHOULD CONTAIN ceil(t) AND NOT CONTAIN ANY SPACING. C(t) =

4. Find the price of a Wednesday call from 6:36 AM (and 12 seconds) until 6:45 AM (and 32 seconds) using LCIs All American Plan ANSWER = $

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