What is the approximate circumference of the circle shown below?

D. 61.2 cm

Step-by-step explanation:

The formula to calculate the circumference of a circle is given by :-

, where d is the diameter of the circle.

In the given picture.,  we have the diameter of circle = 19.5 cm

Then , the circumference of the circle is given by :-

Hence, the circumference of the circle = 61.2 cm

The ratio of 21:63 can be written as a simple ratio of 1:3. It is important you have labels on your numbers.

Here is the ratio rewritten with labels:

21 - old patio: 63 - new patio

1 - old patio: 3 - new patio

This can be switched around to say 3:1 as the ratio of the area of the new to the area of the old.

Each of the number would be square units because they are measuring area.