.It is 12:00 and people are lining up for the matinee at the Bijou Cinema Six. In the first five minutes (12:05), 6 people get into line. At the end of the second five minutes (12:10), there are 11 people in line. At the end of the third five minutes (12:15) there are 16 people in line. If the people keep lining up at this rate, what time will it be when there are 81 people in line?

65 minutes

Step-by-step explanation:

already 16 people in line

total is 81

81 - 16 equals 65

about 5 people every 5 minutes (basically 1 min per person)

so, answer probably 65

1 number

if we use a graphing calculator, there is only one such number that satisfies the conclusion of the mean value theorem, that is, a number such that

where the right-hand side is the average rate of change of f on the interval [0.5,0.75], which is the slope of the secant line.

in the attached graph, the black line is the secant line which has its slope as the average rate of change of f on [0.5,0.75], while the orange line is the only tangent line to the graph of f in the interval that satisfies the mvt conclusion.