Step by step: change 3 into a fraction- 3/1 • 3/4 multiply 3/4 • 3/1 =9/4 = 2 3/4
First one: 0.21
Second one: 0.4
Answer:
The half-life of the radioactive substance is of 3.25 days.
Step-by-step explanation:
The amount of radioactive substance is proportional to the number of counts per minute:
This means that the amount is given by the following differential equation:

In which k is the decay rate.
The solution is:

In which Q(0) is the initial amount:
8000 counts per minute on a Geiger counter at a certain time
This means that 
500 counts per minute 13 days later.
This means that
. We use this to find k.







So

Determine the half-life of the radioactive substance.
This is t for which Q(t) = 0.5Q(0). So







The half-life of the radioactive substance is of 3.25 days.
Answer:2.6
Step-by-step explanation:
Use your graphing calculator of you have one and if you don't you can find one online and plug in the equation and find the intersection . If you get 2.5571 round it to the nearest tenth and you should get 2.6
If you’re looking for a equation it could be “ 24c + 15 = 687 “