Because, well, without them how are you able to add and subtract fractions :D
It is according to the laws of mathematics that you cannot add or subtract fractions that have different denominators to each other. So you need to make your fractions having the same denominator so that they are able to be added or subtracted (hence the equivalent fractions - making the denominators the same are making the fractions equivalent)
Answer: 20.22 is the circumference of the circle
Step-by-step explanation:
Given:
Diameter = 6.45
Radius = 6.45/2 =3.22
To find Circumference:
Circumference = 2r
= 2* 3.14 * 3.22
= 6.28*3.22
=20.22