4/5 = 1/5 + 3/5 is the only answer that I can think of. It's asking for the cumulative property of addition and that's all the information they give you
Last option — a decimal that terminates after three decimal places
Hope this helps good luck u can do thisss :)
Answer:
dy/dt = 7y / (t − 1000)
Step-by-step explanation:
Change in mass of salt = mass of salt going in − mass of salt going out
dy/dt = 0 − (C kg/L × 7 L/min)
where C is the concentration of salt in the tank.
The concentration is mass divided by volume:
C = y / V
The volume in the tank as a function of time is:
V = 1000 + 6t − 7t
V = 1000 − t
Therefore:
C = y / (1000 − t)
Substituting:
dy/dt = -7y / (1000 − t)
dy/dt = 7y / (t − 1000)
If we wanted, we could separate the variables and integrate. But the problem only asks that we find the differential equation, so here's the answer.
We need to know the dimension of the paving stone.
For example, the paving stone is shaped like a rectangular prism with the following dimension.
Length = 10 inches
Width = 3 inches
Height = 2 inches
Volume of a rectangular prism = Length * Width * Height
V = 10 in * 3 in * 2 in
V = 60 in³
60 in³ / 4 in³ = 15
cost of paving stone = 2.50 + .18(15) = 2.50 + 2.7 = 5.20 per paving stone.
