CAT Exam Model Paper 1 with solutions for free online practice

Question : 80 of 100

Marks: +1, -0

If the string is wound on the exterior four walls of a cube of side a cm starting at point C and ending at point D exactly above C, making equally spaced 4 turns. The side of the cube is [Total length of string = 8n cm]

$a = \ { 2 n }/ { √ { 255 } }$
$a = { ( n ) ^ { 2 } }/ { 16 }$
$a = { 8 n } /{ √ { 257 } }$
$a = 2 √ { 15 } n$

Validate

Solution:

Length of string required for 1 turn (or round)

={8n}/4=2n

but

2 n =√ { ( { a } /{ 4 } ) ^ { 2 } + ( 4 a ) ^ { 2 } }

⇒

a = { 8 n } /{ √{ 257 } }

where, a is the side of cube.

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