Answer:

Step-by-step explanation:
Let

Differentiating y with respect to x

where a and b are constants
Formula for the area of a circle:
A = πr² [A = area r = radius]
The radius is
(half) the diameter. Since the diameter = 10cm, the radius = 5cm.
You know:
r = 5cm Substitute/plug this into the equation
A = πr²
A = π(5)²
A = 25π -> A = 25(3.14)
A = 78.5cm²
Answer:
81 m²
Step-by-step explanation:
6x10=60
1/2(6)(7)=21
60+21=81
Answer:
8
Step-by-step explanation:
40 + 5 (at the door)=45
(president's goal) 400 divided by 45= approximately 8