Answer:
[tex]440 = 2\pi {r}^{2} + 2\pi(r)10 \\ [/tex]
[tex]3960 = 2\pi {r}^{2} + 2\pi(r)h[/tex]
[tex] \frac{3960 = 2\pi {r}^{2} + 2\pi(r)h}{440 = 2\pi {r }^{2} + 2\pi(r)10 } [/tex]
[tex]9 = \frac{h}{10} [/tex]
h=90
The height of the cylinder B is 30 cm.
Given that:
Both cylinders A and B are similar. Similarity applies proportionate size which means we have
height of cylinder A : radius of cylinder A :: height of cylinder B: radius of cylinder B
or symbolically we have:
[tex]$\frac{h_1}{r_1} = \frac{h_2}{r_2}$\\[/tex]
or we can say we have:
[tex]r_2 = h_2\times\dfrac{r_1}{h_1} \\[/tex]
Now it is given that Cylinder A's height [tex]h_1[/tex] is 10 cm and surface area is [tex]400\rm \;cm^2[/tex]
Thus from the formula of surface area of cylinder , we have below equation for cylinder A:
[tex]2\pi \times r_1 \times 10 = 440\\or\\r_1 = \dfrac{440}{20\pi}\\\\r_1 \approx 7 \rm\: cm\\\\\\[/tex]
Also given surface area of cylinder B is 3960 [tex]\rm cm^2[/tex], thus:
[tex]2\times \pi\times r_2 \times h_2 = 3960\\\\\2\times\pi\times (h_2\times\dfrac{r_1}{h_1})\times h_2= 3960\\\\2\times\pi\times (h_2\times\dfrac{7}{10})\times h_2 = 3960\\or\\ (h_2)^2 = \dfrac{39600}{2\times\pi\times7}\\\\or\\h_2 = 30 \rm \;cm.[/tex]
Thus height of the cylinder B is 30 cm.
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