When looking for the midpoint of a segment defined by two end points, the average of both coordinates are taken. Averaging the 2 x-coordinates give the new x-coordinate, and the same applies for the y-coordinate. This is shown below:
Midpoint = ( (1 + 4)/2 , (-1 + -6)/2 )
Midpoint = (2.5 , -3.5)
There will be at least 1,350 bacteria in the Petri dish in 3 hours, or at 11:00am.
8:00am: 50 bacteria
9:00am: 150 bacteria
10:00am: 450 bacteria
11:00am: 1350 bacteria
Multiply:
6•12=72
Then, you subtract 39 from 72:
72-39=33
33 containers would still need to be set up.