Answer:
4.5 dollars (before tax id assume)
Answer:
35 pounds of tea for 80 cents.
Step-by-step explanation:
Equation::
value + value = value
80x + 60(50-x) = 74*50
80x + 60*50 - 60x = 74*50
20x = 14*50
x = 35 lbs (amt. of 80 cent tea to use)
50-x = 15 lbs (amt. of 60 cent tean to use)
Start with
Add 2x to both sides:
Subtract 21 from both sides:
Divide both sides by 5. Since it is positive, we don't have to change the inequality sign:
So, the answer is 
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
