30 x 30 = 900
This is the surface area of one side
900 x 6
Multiply by 6 to get the surface area of all 6 sides of the cube
900 x 6 = 5400
<span>Ending Amt = Bgng Amt * e ^-0.03t
In this equation, the "-0.03" is the decay factor or "k"
We can now solve for half-life by this equation:
</span>t = <span>(<span>ln [y(t) ÷ a]<span>)<span> ÷ -k (we can say beginning amount = 200 and ending amount = 100
</span></span></span></span>t = <span>(<span>ln [200 ÷ 100]<span>)<span> ÷ -k
</span></span></span></span>t = <span>(<span>ln [2]<span>)<span> ÷ -k
</span></span></span></span>t = 0.69314718056<span> ÷ --.03
t =</span><span><span><span> 23.1049060187
</span>
about 23 years
</span></span>
It would be 31. 31 is a whole number. since 0.91 is close to 1. We would round it to 31 because of that.
P=2(l + b)
P=2l + 2b
P-2b=2l
P-2b/2=l
C is your answer