Question

If you use a scale factor of 1/5
to create a circle with radius 18 cm, what is the radius of the original circle you dilated?(1 point)
Responses

180 cm
180 cm

9 m
9 m

90 cm
90 cm

3.6 cm

Answer 1

To find the radius of the original circle before dilation, you can use the formula:

\[
\text{Original Radius} = \text{Dilation Radius} \div \text{Scale Factor}
\]

Given a scale factor of \( \frac{1}{5} \) and a radius of the dilated circle as \( 18 \, \text{cm} \):

\[
\text{Original Radius} = 18 \, \text{cm} \div \frac{1}{5} = 18 \, \text{cm} \times 5 = 90 \, \text{cm}
\]

So, the radius of the original circle you dilated is \( 90 \, \text{cm} \).

Therefore, the correct response is:

**90 cm**.