Answer:
k% = 13.8%
Step-by-step Explanation:
To work out the value of [tex]\sf k[/tex], representing the percentage decrease in surface area of statue B ([tex]\sf SA_B[/tex]) compared to statue A ([tex]\sf SA_A[/tex]), given that the volume of statue B is 20% less than the volume of statue A, we can follow these steps:
Volume Relationship:
Given that the volume of statue B ([tex]\sf V_B[/tex]) is 20% less than the volume of statue A ([tex]\sf V_A[/tex]), we have:
[tex]\sf V_B = V_A - 20\% \textsf{ of } V_A [/tex]
[tex]\sf V_B = V_A - \dfrac{20}{100} \times V_A [/tex]
[tex]\sf V_B = V_A - 0.2 V_A [/tex]
[tex]\sf V_B = (1-0.2) V_A [/tex]
[tex]\sf V_B = 0.8V_A [/tex]
Surface Area Relationship for Similar Figures:
For similar figures, the ratio of volumes ([tex]\sf \dfrac{V_B }{ V_A}[/tex]) is related to the cube of the linear scale factor ([tex]\sf k[/tex]), and the ratio of surface areas ([tex]\sf \dfrac{SA_B }{ SA_A}[/tex]) is related to the square of the linear scale factor ([tex]\sf k[/tex]).
Therefore,
[tex]\sf \dfrac{V_B}{V_A} = \left( \dfrac{k}{1} \right)^3 = k^3 [/tex]
[tex]\sf \dfrac{SA_B}{SA_A} = \left( \dfrac{k}{1} \right)^2 = k^2 [/tex]
Calculate [tex]\sf k[/tex]:
Substitute [tex]\sf V_B = 0.8 \times V_A[/tex] into the volume ratio equation:
[tex]\sf \dfrac{0.8 \cancel{V_A}}{\cancel{V_A}} = k^3 [/tex]
[tex]\sf 0.8 = k^3 [/tex]
Taking the cube root of both sides to solve for [tex]\sf k[/tex]:
[tex]\sf k = \sqrt[3]{0.8} \approx 0.9283177667 [/tex]
Calculate [tex]\sf k\%[/tex] (Percentage Decrease in Surface Area):
Now, calculate [tex]\sf k\%[/tex] which represents the percentage decrease in surface area:
[tex]\sf k\% = (1 - k^2) \times 100\% [/tex]
[tex]\sf k\% = (1 - (0.9283177667)^2) \times 100\% [/tex]
[tex]\sf k\% = (1 - 0.861773876) \times 100\% [/tex]
[tex]\sf k\% = 0.138226124 \times 100\% [/tex]
[tex]\sf k\% = 13.8226124\% [/tex]
[tex]\sf k\% \approx \boxed{13.8\%}\textsf{(in 3 significant figures)}[/tex]
Therefore, [tex]\sf k \approx \boxed{13.85\%}[/tex], indicating that the surface area of statue B is approximately 13.8% less than the surface area of statue A, consistent with the given volume relationship between the two statues.