Answer: OPTION D
Step-by-step explanation:
The formula for calculate the surface area of a rectangular prism is:

Where w is the width, h is the height and l is the length.
You can see in the figure attached that:
l=3.4ft
w=3ft
h=4.1ft
Therefore, when you substitute these values into the formula you obtain that the surface area is:
![SA_{rp}=2[(3ft*4.1ft)+(3.4ft*3ft)+(3.4ft*4.1ft)]=72.88ft^{2}](https://tex.z-dn.net/?f=SA_%7Brp%7D%3D2%5B%283ft%2A4.1ft%29%2B%283.4ft%2A3ft%29%2B%283.4ft%2A4.1ft%29%5D%3D72.88ft%5E%7B2%7D)
V = (1/4)(π* d² * h)
<span>V = (1/4)(π * 10² * 12) </span>
<span>V = (1/4)(1200π) </span>
<span>V = 300π </span>
<span>[ V ≈ 942 cubic units . . . . . to 3 s.f. ] </span>
<span>V ≈ 942 cubic units
</span>
The area of a circle is A = πr^2. We let A1 And A2 the areas of the circles and r1 and r2 the radius of each, respectivley.
A1 + A2 = 80π
Substitute the formula for the area,
π(r1)^2 + π (r2)^2 = 80π
From the statement, we know that r2=2(r1).
<span>π(r1)^2 + π (2 x r1)^2 = 80π
</span>We can cancel π, we will have
5 x (r1)^2 = 80
Thus,
r1 = 4 and r2 = 8
Answer:
Marco's age is 7 years old
Step-by-step explanation:
Let
x ----> Marco's age
y ----> Paolo's age
we know that
---->
----> equation A
----> equation B
substitute equation A in equation B


Solve the quadratic equation
The formula to solve a quadratic equation of the form
is equal to

in this problem we have

so

substitute in the formula





Remember that the solution cannot be a negative number
so
The solution is x=7
therefore
Marco's age is 7 years old