SOLUTION: solve A) the circumference of a circle is 2,500 cm. Find its diameter and its area ( approximate to nearest tenth place.) B) An electrician wants to cut a 30-foot electric wire i

Question 172841: solve
A) the circumference of a circle is 2,500 cm. Find its diameter and its area ( approximate to nearest tenth place.)
B) An electrician wants to cut a 30-foot electric wire into 3 pieces. The longest piece is to be four times as long as the shortest and the middle-sized piece is to be 2 feet less than three times the shortest piece. Write the equation. And find the length of each of the pieces.
Found 2 solutions by colliefan, checkley77:
Answer by colliefan(242) (Show Source): You can put this solution on YOUR website!
You need the equations for circumference and area of a circle.
C = 2 * pi * r
and
A = pi * r^2

Changing the first equation so that you can solve for the radius if you know the circumference gives you:
C / (2 * pi) = r
If the circumference of the circle is 2500 cm, the radius = 2500/(2*pi). Substituting 3.1415 in for pi will give you the number.

Now that you have the radius, you can calculate the area as pi * r^2.

The 3 pieces of wire have to total a length of 30 ft. If the shortest length is x, then we could write the length of the longest piece as 4x and the length of the middle-sized piece as 3x-___ . Fill in the blank with the number from the problem. (It is missing in your question. Since the length of the 3 pieces equals 30, the equation to solve is:
x + 4x + 3x-___ = 30
Once you solve for x, you can calculate the lenghts of the 3 pieces.
Answer by checkley77(12844) (Show Source): You can put this solution on YOUR website!
A)
2,500=pi*d
2,500=3.14d
d=2,500/3.14
d=796.2 cm is the diameter.
a=pir^2
a=3.14(796.2/2)^2
a=3.14*398.1^2
a=3.14*158,483.6
a=497,638.5 cm^2 is the area.
B) An electrician wants to cut a 30-foot electric wire into 3 pieces. The longest piece is to be four times as long as the shortest and the middle-sized piece is to be 2 feet less than three times the shortest piece. Write the equation. And find the length of each of the pieces.
L=4S
M=3S-2
L+M+S=30
4S+3S-2+S=30
8S=30+2
8S=32
S=32/8
S=4 feet for the shortest length.
L=4*4=16 feet for the longest.
M=3*4-2=12-2=10 feet for the middle one.
Proof:
4+16+10=30
30=30

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