Answer:
the rate of change in volume is dV/dt = 4π mm³/s = 12.56 mm³/s
Step-by-step explanation:
since the volume V of a cylinder is related with the height H and the radius R through:
V = πR²*H
then the change in time is given by the derivative with respect to time t
dV/dt = (∂V/∂R)*(dR/dt) + (∂V/∂H)*(dH/dt)
the change in volume with radius at constant height is
(∂V/∂R) = 2*πR*H
the change in volume with height at constant radius is
(∂V/∂H) = πR²
then
dV/dt = 2π*R*H *(dR/dt) + πR²*(dH/dt)
replacing values
dV/dt = 2π* 2 mm * 20 mm * (-0.1 mm/s) + π (2 mm) ²* 3 mm/s = 4π mm³/s
dV/dt = 4π mm³/s = 12.56 mm³/s
Answer:
25 more boxes is needed
Step-by-step explanation:
12000 batteries require 50 boxes. Let's find the unit rate.
That is, how many batteries are in each box??
That's 12,000/50!
12,000/50 = 240 batteries per box
Now, to find how many boxes we would need for 18,000 batteries, we will have to divide the total (18000) by 240(number of batteries per box). That is:
18,000/240 = 75 boxes
We would need 75 boxes to pack 18,000 batteries.
We want "how many MORE boxes needed", so we will the excess:
75 - 50 = 25 more boxes is needed
Let Ted be x.
Ed is 7 years older = x + 7
Ed = (3/4)Ted
(x + 7) = (3/4)x
x + 7 = 3x/4
x - 3x/4 = -7
x/4 = -7
x = -28, Ted = -28 years.
(x + 7) = -28 + 7 = -21, Ed = -21 years
Goodness. We had negative numbers for the ages, well does that make sense? No it doesn't.
Our answer is correct. But the sense in the question is lacking. The question has been wrongly set.
<span>We might assume negative ages to mean before they came into the world, before birth! </span>
