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8th Class Mathematics Cubes and Cube Roots Question Bank Cube and Cube Roots

  • question_answer
    Three numbers are in the ratio to one another 2:3:4 and the sum of their cubes is 33957. What are the numbers?

    A)  21, 14, 28                    

    B)  14, 21, 28

    C)  28, 14, 21                    

    D)  27, 15, 14

    Correct Answer: B

    Solution :

    (b): Let no. s be \[2x,3x,4x\] \[{{\left( 2x \right)}^{3}}+{{\left( 3x \right)}^{3}}+{{\left( 4x \right)}^{3}}\] \[=\left( 8+27+64 \right){{x}^{3}}\] \[=99{{x}^{3}}\] Also, \[99{{x}^{3}}=33957\] \[{{x}^{3}}=343\]    \[x=7\] Nos are \[2\times 7,3\times 7,4\times 7.\]


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