Question

$A$ and $B$ are two points and $C$ is any point collinear with $A$ and $B$. IF $AB=10$, $BC=5$, then $AC$ is equal to:

• A. either $15$ or $5$
• B. necessarily $5$
• C. necessarily $16$
• D. none of these

Answer 1

The correct option is A either $15$ or $5$

Since $C$ is collinear with $A$ and $B,C$ lies either
(i) to the left of point B or
(ii) to the right of point B
$\therefore$ In case (i) $AC=AB-BC=10-5=5$
In case (ii) $AC=AB+BC=10+5=15$