The required equation of the surface area of the cylinder is 
<u>Solution:</u>
Let "r" be the radius of cylinder and "h" be the height.
Formula for surface area is:

where
is surface of two bases of cylinder and
is surface of mantle.
From the given, the height of the gift box is three times the radius, i.e 
On substituting the given values in the formula we get,
![S = 2\times\pi[(3x+4)^2 + (9x+12)\times(3x+4)]](https://tex.z-dn.net/?f=S%20%3D%202%5Ctimes%5Cpi%5B%283x%2B4%29%5E2%20%2B%20%289x%2B12%29%5Ctimes%283x%2B4%29%5D)
![\Rightarrow S=2\pi[(3x^2)+2\times3x\times4+4^2]+[(9x\times3x)+12\times3x+36x+48]](https://tex.z-dn.net/?f=%5CRightarrow%20S%3D2%5Cpi%5B%283x%5E2%29%2B2%5Ctimes3x%5Ctimes4%2B4%5E2%5D%2B%5B%289x%5Ctimes3x%29%2B12%5Ctimes3x%2B36x%2B48%5D)
![\Rightarrow S=2\pi[9x^2+24x+16]+[21x^2+36x+36x+48]](https://tex.z-dn.net/?f=%5CRightarrow%20S%3D2%5Cpi%5B9x%5E2%2B24x%2B16%5D%2B%5B21x%5E2%2B36x%2B36x%2B48%5D)
![\Rightarrow S=2\pi[9x^2+24x+16+21x^2+72x+48]\rightarrow2\pi[30x^2+96x+64]](https://tex.z-dn.net/?f=%5CRightarrow%20S%3D2%5Cpi%5B9x%5E2%2B24x%2B16%2B21x%5E2%2B72x%2B48%5D%5Crightarrow2%5Cpi%5B30x%5E2%2B96x%2B64%5D)
On multiplying
inside the brackets we get,
![\Rightarrow S=[60\pi x^2+192\pi x+128\pi]](https://tex.z-dn.net/?f=%5CRightarrow%20S%3D%5B60%5Cpi%20x%5E2%2B192%5Cpi%20x%2B128%5Cpi%5D)
Hence, the required equation is 
Answer:
1)20 000 000×12cm
240 000 000/100m
240 000 0/1000
2400km
31.6--1580×100×1000
31.6--1580 00 000
31.6/31.6--1580 00 000/31.6
1:5000000