Match each equation to the situation it represents. Situation
Equation
Leilah has not yet studied 600 of her 2400 flashcards. She studies 40 new
cards each day.
2400 - 400 = 600
Stetson rents studio space for $600 a month for music lessons. He charges
his students $40 per hour and earned a profit of $2400 this month.
(600 + 40)2 = 2400
A kit contains 600 letter tiles and 40 number tiles. Each tile has the same
mass, and the kit has a total mass of 2400 g.
400 - 600 = 2400

Aprisoner is trapped in a cell containing three doors. the first door leads to a tunnel that returns him to his cell after two days of travel. the second leads to a tunnel that returns him to his cell after three days of travel. the third door leads immediately to freedom. (a) assuming that the prisoner will always select doors 1, 2 and 3 with probabili- ties 0.5,0.3,0.2 (respectively), what is the expected number of days until he reaches freedom? (b) assuming that the prisoner is always equally likely to choose among those doors that he has not used, what is the expected number of days until he reaches freedom? (in this version, if the prisoner initially tries door 1, for example, then when he returns to the cell, he will now select only from doors 2 and 3.) (c) for parts (a) and (b), find the variance of the number of days until the prisoner reaches freedom. hint for part (b): define ni to be the number of additional days the prisoner spends after initially choosing door i and returning to his cell.