9th Class Mathematics Linear Equations in Two Variables Question Bank Linear Equations in Two Variables

  • question_answer A and B are friends. A is elder to B by 5 years. B's sister C is half the age of B while A's father D is 8 years older than twice the age of B. If the present age of D is 48 years, find the present ages of A, B and C respectively.

    A)  50 years, 25 years, 20 years

    B)  40 years, 20 years, 15 years

    C)  20 years, 15 years, 10 years

    D)  25 years, 20 years, 10 years                                                                                                       

    Correct Answer: D

    Solution :

    Let the present ages of A, B, C and D are \[x,y,z\]and t respectively. Since, present age of D = t = 48 years. According to question, \[x=y+5\]                                             ?(i) \[z=\frac{1}{2}y\]                                                          ?(ii) \[t=2y+8\]                                            ?(iii) From (iii), \[48=2y+8\] \[\Rightarrow \]   \[2y=40\Rightarrow y=20\]years From (ii), \[x=\frac{1}{2}\times 20=10\]years From (i), \[x=20+5=25\]years So, present ages of A, B and C are 25 year, 20, years and 10 years respectively.

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