Answer:
The rate of change is 
ft^(2)/min
Step-by-step explanation:
The area of a circle is given by the following equation:
To solve this question, we have to realize the implicit differentiation in function of t. We have two variables, A and r. So
We have that:
.
We want to find 
So
Since the area is in square feet, the rate of change is in ft^(2)/min.
So the rate of change is ft^(2)/min
Answer:
Step-by-step explanation:
Let s represent the son's age now. Then s+32 is the father's age. In 4 years, we have ...
5(s+4) = (s+32)+4
5s +20 = s +36 . . . . . eliminate parentheses
4s = 16 . . . . . . . . . . . . subtract s+20
s = 4
The son is now 4 years old; the father, 36.
_____
<em>Alternate solution</em>
In 4 years, the ratio of ages is ...
father : son = 5 : 1
The difference of their ages at that time is 5-1 = 4 "ratio units". Since the difference in ages is 32 years, each ratio unit must stand for 32/4 = 8 years. That is, the future age ratio is ...
father : son = 40 : 8
So, now (4 years earlier), the ages must be ...
father: 36; son: 4.
Step-by-step explanation:
3y + x = 12
When y = 3, we have 3(3) + x = 12.
=> 9 + x = 12, x = 3.
