8th Class Mathematics Mensuration Question Bank Mensuration

  • question_answer If two cubes of sides 9 cm each are joined end by end then the surface area of cuboid will

    A)  800 \[c{{m}^{2}}\]                

    B)  810 \[c{{m}^{2}}\]   

    C)  820 \[c{{m}^{2}}\]                

    D)  830 \[c{{m}^{2}}\]

    Correct Answer: B

    Solution :

    (b): As we know, surface area \[=6{{a}^{2}}\] Two cubes joined \[\Rightarrow \]Total surface area \[=2\times 6{{a}^{2}}-\] surface area of two cubes at joints \[\Rightarrow 12{{a}^{2}}-2\times {{a}^{2}}=10{{a}^{2}}=10\times {{9}^{2}}=810.\]


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