Answer:

if you insert x and y values in equation you can find the exact equation
Linear equation with a negative rate of change because the balance would decrease by the same amount each day.
3 to the 4th power is 81, 3 times itself 4 times.
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The statement "the diagonals are perpendicular ti each other" is sometimes true and sometimes false
Question 1)
I assume it asks about the circumference (of only the circle arc)
C=r*2*pi
r=2
-> C=4pi
1 Quarter only of the circle: C/4=pi=3.1
if it's the perimeter of the shape then you need to add the two 2in sides
C=3.1+2*2=7.1
2)
C=r*2*pi, but not a full circle, only semi-> divide by 2-> C=r*pi
r=30
C=30pi=94.2
3)
the radius of the semicircle is 6/2=3mm
semicircle C=r*pi=3pi
add the rectangle perimeter
3pi+2*3+6=12+3pi=21.4
4)
C=2r*pi
insert 2r=d=12
C=12pi=37.7
5)
C=2r*pi
r=10
C=20*pi~62.8
3 rotations of the wheel->
distance=C*3=188.4