A fire drill will begin at a randomly-chosen time
between 8:30 a.m. and 3:30 p.m. You have a math test planned for 2:05 p.m. to 3:00 p.m. If the fire drill is in the afternoon, what is the probability that it will start during the test?

Question

A fire drill will begin at a randomly-chosen time 
between 8:30 a.m. and 3:30 p.m. You have a math test planned for 2:05 p.m. to 3:00 p.m. If the fire drill is in the afternoon, what is the probability that it will start during the test?

ganeshie8 · Answer

Event A :  firedrill to start in afternoon
Event B : firedrill to start during test

ganeshie8 · Answer

P(B | A) =  25minutes /(3*60+30)minutes =  25/210 = 5/42

highschoolmom2010 · Answer

attachment

highschoolmom2010 · Answer

any ideas how my book got 11/42

ganeshie8 · Answer

okay, ur textbook is correct again. i made a mistake

ganeshie8 · Answer

mistake in counting # of minutes the test takes :/

ganeshie8 · Answer

how many minutes are there between :  2:05 p.m. to 3:00 p.m

?

highschoolmom2010 · Answer

55

ganeshie8 · Answer

yes, 
and how many minutes are there between "afternoon" and "3:30" ?

ganeshie8 · Answer

btw, noon = 12:00

ganeshie8 · Answer

12 to 3:30
that 3 and half hours right ?

highschoolmom2010 · Answer

210

ganeshie8 · Answer

yes, 
so probability for the drill to occur during test, given that drill occured after noon :-

P(B | A) =  55/210

ganeshie8 · Answer

simplify

highschoolmom2010 · Answer

oh ok that makes more sense now

highschoolmom2010 · Answer

ty @ganeshie8

ganeshie8 · Answer

np :)