Ex.11.3 Q4 Mensuration Solution - NCERT Maths Class 8

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Rukhsar painted the outside of the cabinet of measure \(1\,\rm{m} \times 2\, \rm{m} \times \,1.5\, \rm{m.}\) How much surface area did she cover if she painted all except the bottom of the cabinet?

 Video Solution
Ex 11.3 | Question 4

Text Solution

What is Known?

Dimensions of the cuboid.

What is unknown?

 Surface area of cuboid that was palindrome.


Surface area of bottom of the cuboid will be subtracted from the total surface area of the cabinet.


Length (\(l\)) of the cabinet \(=\,2\,\rm{m}\)

Breadth (\(b\)) of the cabinet \(=1\,\rm{m}\)

Height (\(n\)) of the cabinet \(= 1.5\,\rm{m}\)

Area of the bottom of cabinet \( = (l \times b)\)

Total Surface area of the cabinet \( = 2(l \times b + b \times h + n \times l)\)

Area of the cabinet that was painted \(=\) (Total surface area of  the cabinet) \(-\) (Area of bottom of the cabinet)

\[\begin{align} &= 2(l \times b + b \times h + h \times l) - l \times b\\&= 2(b \times h + h \times l) + l \times b\\ &= [2 \times (1 \times 1.5 + 1.5 \times 2) + 2 \times 1]\,{{\rm{m}}^2}\\&= [2 \times 4.5 + 2]\,{{\rm{m}}^2}\\&= 11\,{{\rm{m}}^2} \end{align}\]

Hence, the required area \(= 11 \,\rm{m}^2\)

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