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:

Answer:
8h=30
Lizbeth can not climb for 4.5 hours.
Step-by-step explanation:
If you plug in 4.5 for h you get
8(4.5)=30
36 does not equal 30
Therefore Lizbeth can't climb for 4.5 hours
Answer:
Of all 6 faces it would be 150
Step-by-step explanation:
If one side of the cube is 5cm long, then l × w = area of a face, so if it is a cube then all 4 sides are the same on a face so 5 × 5 = 25, so 25 × 6 faces = 150
Answer:
5h 15 min
Step-by-step explanation:
70 mph * 4,5 = 315 miles
315 / 60 = 5,25h
5,25h = 5 1/4h = 5h 15 min