Answer:
idk im not that smart
Step-by-step explanation:
Given:
- Height of cylinder is 18.2 cm
- Radius of cylinder is 3 cm

To Find?

Solution:
Using formula:
- Surface area of cylinder = 2πr (h + r)

Substituting values in the formula:





- Hence, (B) 399.4 cm² is right answer.
Answer:
a)
, b)
, c)
, d) 
Step-by-step explanation:
a) Let assume an initial mass m decaying at a constant rate k throughout time, the differential equation is:

b) The general solution is found after separating variables and integrating each sides:

Where
is the time constant and 
c) The time constant is:


The particular solution of the differential equation is:

d) The amount of radium after 300 years is:

I believe the answer is B because you distribute 4(x-8) to get 4x-32 and distribute 7(x-4) to get 7x-28