The amount of a radioactive substance decreases by 10% every
12 hours. Currently the amount of substance is 100 grams. If n is
a whole number, which expression represents the number of
grams of substance left n days from now?
A.100(0.81)^n
B.100(1.1)^2n
C.100(0.81)^n/2
D.100(0.8)^n

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step-by-step explanation:

area of rectangle a is 2 times that of rectangle b that means 2x+x =   36cm^2

3x = 36cm ^2

x = 36/3

x= 12cm^2

and 2x = 24cm^2

now side of square = are divided by sides = 36/4 = 6cm

that means length of rectangle a and b is 6cm too

now for rectangle a,

l*b = area

= 6*y=24

y=24/6 = 4

therefore dimensions of rectangle a are- length = 6cm, breadth = 4cm

and for rectangle b, length = 6cm and breadth = 6-4 = 2cm.

hope this .