Pointsto Consider
Someeventsare morelikely, and someare less likely. No eventhas a negativeprobability!Can you think
of an eventwith an extremelylow, or an extremelyhigh,probability?Whatare the ultimateextremes—the
greatestand the leastvaluespossiblefor a probability?In ordinarylanguagetheseare called“impossible”
(leastpossibleprobability)and “certain”or a “surething”(greatestpossibleprobability).
The studyof probabilityoriginatedin the seventeenthcenturyas mathematiciansanalyzedgamesof chance.
For FurtherReading
FrenchmathematiciansPierrede Fermatand BlaisePascalare creditedas the “inventors”of mathematical
probability. The referencebelowis an easyintroductionto their ideas.
http://mathforum.org/isaac/problems/prob1.html
LessonExercises
- Rita is retired.For her, everyday is a holiday. Whatis the probabilitythat tomorrowis a holidayfor Rita?
- Chazis “on call” any time,any day. He neverhas a holiday. Whatis the probabilitythat tomorrowis a
holidayfor Chaz? - The only thingson Ray’s refrigeratordoor are greenmagnetsand yellowmagnets.Ray takesone
magnetoff withoutlooking.
a. Whatis the probabilitythat the magnetis green?b. Whatis the probabilitythat the magnetis yellow?c. Whatis the probabilitythat the magnetis purple?Ray takesoff two magnetswithoutlooking.
d. Whatis the probabilitythat both magnetsare green?e. Whatis the probabilitythat Ray takesoff one greenand one yellowmagnet?- Reedusesthe diagrambelowas a modelof a highway.
Reedgot a call aboutan accidentat an unknownlocationbetweenActonand Dayton.
a. Whatis the probabilitythat the accidentisnotbetweenCantonand Dayton?b. Whatis the probabilitythat the accidentis closerto Cantonthan it is to Barton?- A tire has an outerdiameterof inches.Ninanoticeda weakspot on the tire. She markedthe weak
spot with chalk.The chalkmarkis inchesalongthe outeredgeof the tire. Whatis the probabilitythat part
of the weakspot is in contactwith the groundat any time?