Question

Percentages of free space in cubic close packed structure and in body centered packed structure are respectively.

• A. 30% and 26%
• B. 26% and 32%
• C. 32% and 48%
• D. 48% and 26%

Answer 1

Answer: (B)

26% and 32%

Answer 2

Packing fraction of CCP = $\frac{\pi}{3\sqrt{2}}$= 0.74 $\Rightarrow$ 74%

\ Percentage of free space in CCP = 100 – 74 = 26%

Packing fraction of BCC = $\frac{\pi\sqrt{3}}{8}$ = 0.68 $\Rightarrow$ 68%

\ Percentage of free space in BCC = 100 – 68 = 32%