Alexandra is scuba diving. A diving computer automatically records her depth every five minutes. The depth readings from her first 20 minutes of diving are shown in the table below. Elapsed time (in minutes)
Depth (in meters)
0
0
5
–12.45
10
–9.7
15
–22.98
20
–6.6

Which best represents the greatest amount of change in her depth over a single 5-minute period?

192/15 = 12.8.

12.8

step-by-step explanation:

192/15 is 12.8.

however, it says to round to the nearest foot, which would equal 13.

ending amount = beginning amount / (2^n)

where "n" = number of half-lives (or elapsed time / half-life)

ending amount = 50 mg / (2 ^10 / 5.3)

ending amount = 50 mg / (2 ^ 1.8867924528)

ending amount = 50 m / 3.6981210597

ending amount = 13.5203794557 mg

or about 13.5 mg remain

source: