Circumference of a circle - derivation
This page describes how to derive the formula for the circumference of a circle.
Recall that the definition of pi (π) is the circumference c of any circle divided by its diameter d. Put as an equation, pi is defined as
π
=
c
d
Rearranging this to solve for c we get
c
=
π
d
The diameter of a circle is twice its radius, so substituting 2r for d
c
=
2
π
r
If you know the area
Recall that the area of a circle is given by
area
=
π
r
2
Solving this for r
r
2
=
a
π
So
r
=
√
a
π
The circumference c of a circle is
c
=
2
π
r
Answer:
21 students pass
Step-by-step explanation:
Firstly, you can set up the problem into an equation where the variable X would equal the number of students passing. You put X over the total number of students in the class, turning it into a fraction, then set it equal to the fraction 
(which is 75% represented as a fraction).
The fraction can be simplified, because 75 and 100 are both multiples of 25, so after canceling out the 25s you would be left with 
.
Next, you use the process of cross multiplication which is essentially just multiplying the denominators of both fractions (which would be 28 and 4 in this case) to each side of the equation.
The denominators cancel out leaving you with a simple equation to simplify.
Finally, divide both sides by four in order to isolate the variable.
X = 21.
Answer:
60 degrees
Step-by-step explanation:
If each side of the triangle WRD is 3 inches long, then WRD is an equilateral triangle, meaning all angles are the same size. Since there are 180 degrees in a triangle, 180/3 = 60 degrees.
(1928912×192) ÷ (182×9) + 4- (12378923789×-52)
= 6.437042e11
Answer:
7/30
Step-by-step explanation:
