MCQ
If the points $A(3,{\rm{ }}4),\,B(7,{\rm{ }}7),\,C(a,{\rm{ }}b)$ be collinear and $AC = 10$, then $(a,{\rm{ }}b)$=
  • $(11,{\rm{ }}10)$
  • B
    $(10,{\rm{ }}11)$
  • C
    $(11/2,\,5)$
  • D
    $(5,{\rm{ }}11/2)$

Answer

Correct option: A.
$(11,{\rm{ }}10)$
a
(a) ${(a - 3)^2} + {(b - 4)^2} = 100$ and $\frac{{b - 7}}{3} = \frac{{a - 7}}{4}$

Hence $(a, b)$=$(11, 10)$.

Trick : Check with options. We find that the point $(11, 10)$ satisfies both the conditions i.e. $AC = \sqrt {{{(11 - 3)}^2} + {{(10 - 4)}^2}} = 10$.

Also this is collinear with $A,\,B$.

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