The data table below shows a person’s heart rate measured in beats per minute (bpm) at five different times in the beginning of a day. What causes the change in heart rate over time? 1. tired
2. increased activity
3. passing of time
4. forgetting to eat

Atank contains 240 liters of fluid in which 10 grams of salt is dissolved. brine containing 1 gram of salt per liter is then pumped into the tank at a rate of 6 l/min; the well-mixed solution is pumped out at the same rate. find the number a(t) of grams of salt in the tank at time t.

Aballoon inflated with three breaths of air has a volume of 1.7 l. at the same temperature and pressure, what is the volume of the balloon if five more same-sized breaths are added to the balloon?

Asample of radium-226 will decay 1/4 of its original amount after 3200years. what is the half-life of radium-226?