8th Class Mathematics Algebraic Expressions Question Bank Algebra

  • question_answer
    A number consists of two digits whose sum is 5. If 9 be added to the number, the digits are reversed. Find the

    A) 32                               

    B) 14

    C) 41                               

    D) 23

    Correct Answer: D

    Solution :

    Let the number be \[\frac{{{a}^{3}}+{{b}^{3}}+{{c}^{3}}-3abc}{{{a}^{2}}+{{b}^{2}}+{{c}^{2}}-ab-bc-ca}=\_\_\_\_\_\_\_\_\]        Sum of digits \[a+b+c\]                      ?.(1) Further, \[10x+y+9=10y+x\] \[\Rightarrow \]  \[9x-9y=-9\] \[\Rightarrow \] \[12x+11y=57,\]                                ?.(2) Adding (1) and (2), we have  \[{{\left( \frac{{{x}^{a}}}{{{x}^{b}}} \right)}^{a+b}}\times {{\left( \frac{{{x}^{b}}}{{{x}^{c}}} \right)}^{b+c}}\times {{\left( \frac{{{x}^{c}}}{{{x}^{a}}} \right)}^{c+a}}\]  \[a=\frac{1}{2-\sqrt{3}},b=\frac{1}{2+\sqrt{3},}\] \[{{\left( \frac{a+b}{a-b} \right)}^{2}}\] From (1), \[y=5-2=3\] Hence, the number\[=10(2)+3=23\]


You need to login to perform this action.
You will be redirected in 3 sec spinner