Coordinate Geometry Question - CBSE

Question

If $P\left(\dfrac{a}{3}, 4\right)$ is the midpoint of the line segment joining the points $Q(-6, 5)$ and $R(-2, 3)$, then the value of $a$ is:
(a) $-4$
(b) $-12$
(c) $12$
(d) $-6$

Accepted Answer

$\dfrac{a}{3} = \dfrac{-6 + (-2)}{2} = \dfrac{-8}{2} = -4$. [0.5 Mark]
$a = 3 imes (-4) = -12$. [0.5 Mark]

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🎯 Official CBSE Marking Scheme:
Midpoint x-coordinate equation setup: 0.5 Mark
Solving for $a = -12$: 0.5 Mark

Question:

Step-by-Step Solution

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