Longest diagonal of the room =√l2+b2+h2 Where, 1= length, b= breadth and h= height Let the value of Height =12 According to the question Then, Breadth =(
4
3
×12)=16 Length =(
21
16
×16)=21 Now, longest diagonal of the room =√(12+b2+h2) ⇒L=√(212+162+122) ⇒L=√(441+256+144) ⇒L=√841 ⇒L=29 Now, ⇒