A) \[3\sqrt{2}\]cm
B) \[2\sqrt{5}\]cm
C) \[4\sqrt{5}\]cm
D) \[5\sqrt{5}\]cm
Correct Answer: C
Solution :
Radius = R cm \[4=\sqrt{{{R}^{2}}-16}-\sqrt{{{R}^{2}}-64}\] \[\Rightarrow \,\] \[\sqrt{{{R}^{2}}-16}=4+\sqrt{{{R}^{2}}-64}\] \[\Rightarrow \,\] \[{{R}^{2}}-16=16+{{R}^{2}}-64+8\sqrt{{{R}^{2}}-64}\] \[\Rightarrow \,\] \[32=8\sqrt{{{R}^{2}}-64}\] \[\Rightarrow \,\] \[{{R}^{2}}-64=16\] \[\Rightarrow \,\] \[{{R}^{2}}=80\] \[\therefore \] \[R=4\sqrt{5}\]You need to login to perform this action.
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