#5) 7.065 sq. ft.
#6) 36 ft
#7) 200.96 sq. ft.
#8) 176.625 sq. ft.
Explanation
#5) Converting 18 inches to feet, 18/12 = 1.5. The area of the circle would be given by A=3.14(1.5)² = 3.14(2.25) = 7.065 sq. ft.
#6) The radius is 18 inches, so the diameter is twice that: 18*2 = 36 inches. Converting this to feet, we have 36/12 = 3 feet. Each stone is 3 feet across. Laying 12 of them against each other would give us a total length of 12*3 = 36 feet.
#7) The radius of the entire mirror with frame is 20/2 = 10. The area of the entire mirror with frame is A=3.14(10²) = 3.14(100) = 314 in².
The area of the mirror without the frame is A=3.14(6²) = 3.14(36) = 113.04 in².
The difference between the two will give the area of the frame:
314-113.04 = 200.96 in²
#8) The area of the circular region is given by A=3.14(7.5²) = 176.625 ft²
The answer
5
Explanation
The shape is a pentagon
The conditional, <span>If four points are non-coplanar, then they are non-collinear, </span>is true:
This is, coplanarity is a necessary condition to be collinear.
The converse, <span>If four points are non-collinear, then they are non-coplanar, is false.
A counterexample that disproves this statement is the 4 vertices of a paralelogram, of course they are in a same plane and are not collinear.
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