561 Worksheet
1. Assume that your kidneys can filter out 25% of medicine in your blood every 4 hours. You take one
1000-milligram dose of the medicine. Fill in the table showing the amount of the medicine in your
blood as a function of time. The first three data points are already completed.
At first you will have decimals. Round each value to the nearest milligram so there are no
decimals in your answers.
Time since taking the medicine (in hours)
Amount of medicine in blood (in milligrams)
0
1000
4
1000 - (1000 x 0.25) = 750
8
750 - (750 x 0.25) = 562.5 563
12
16
20
24
28
32
36
40 44 48 52 56

12

563 - (563x0.25) = 422.25 -> 422

16

422 -(422x0.25) = 316.5 -> 317

20

317 - (317x0.25) = 237.75 -> 238

24

238 - (238x0.25) = 178.5 -> 179

28 (continue the step by step process)

134.25 -> 134

32

100.5 -> 101

36

75.75 -> 76

40

57

44

42.75 -> 43

48

32.25 -> 32

52

24

56

18

Step-by-step explanation:

the time interval has to keep skipping by four hours because the medicine is filtered in that amount of time.

The multiplying by 0.25 part must be done first in order to show how much the kidney has filtered.

after this, you need to subtract that from how many milligrams of medicine are left in your system

note that if you do not subtract, you will only be showing how much the kidney has filtered. the question asks for how much is left in the SYSTEM overall, so subtracting is quite necessary to completely answer the question.

I hope this helped.