Cone a and cone b both have a height of 5 in. The volume of cone a is 20.9cubic in, the volume of cone b is 4 times the volume of cone a, about how many times longwr is the diameter of cone b than the diameter of cone a?

Respuesta :

Answer: two times

Step-by-step explanation:

Given

height of cone A and B  [tex]h_a=h_b=5\ in.[/tex]

The volume of cone A  [tex]V_a=20.9\ in.^3[/tex]

The volume of cone B is 4 times of cone A

the volume of a cone is  [tex]\frac{1}{3}\pi r^2h[/tex]

The volume of cone A

[tex]V_a=\dfrac{1}{3}\pi r_a^2h_a=20.9\quad \ldots(i)[/tex]

The volume of cone B

[tex]V_b=\dfrac{1}{3}\pi r_b^2h_b=4\times 20.9\quad \ldots(ii)[/tex]

divide (i) and (ii) we get

[tex]\Rightarrow \dfrac{r_a^2}{r_b^2}=\dfrac{1}{4}\\\Rightarrow \dfrac{r_a}{r_b}=\sqrt{\dfrac{1}{4}}=\dfrac{1}{2}\\\Rightarrow \dfrac{d_a}{d_b}=\dfrac{1}{2}\\\Rightarrow d_b=2d_a[/tex]

thus, diameter of cone B is twice the diameter of A