Question

A triangle ABC is enlarged, about the point O as centre of enlargement, and the scale factor is 3. Find OC', if OC=21 cm.

• A. 63 cm
• B. 53 cm
• C. 43 cm
• D. none of the above

Answer 1

The correct option is A 63 cm

$△ABC$ is enlarged to $△A^{\prime }{B}^{\prime }{C}^{\prime }$,
Thus, $\frac{O{C}^{\prime }}{OC}=3$
$\Rightarrow \frac{O{C}^{\prime }}{21}=3$
$\Rightarrow O{C}^{\prime }=21\times 3$
$\Rightarrow O{C}^{\prime }=63$ cm