Circles: Circumference to diameter relationship ?

Question

Just two simple questions:(i didn't find to simple)

"For circle, every time the diameter is doubled, the circumference will be multiplied by:___?"

"For a circle, every time the diameter increases by 1 unit, the circumference will increase by:___?"

i just need to know those two relationships.

thanks

Answer 1

everytime diamete x2 => circumference increase by 2

diameter by 1 unit=> circum increase by pie