Question

a circle’s circumference is proportional to its diameter. definition: let x and y denote two quantities. then y ______ with x, or y is directly proportional to x, if there is a nonzero number k for which __. the number k is called the ______.

Explanation:

For direct proportionality, the first blank is "varies directly" as per the definition. The formula for direct proportion is \( y = kx \) (where \( k
eq0 \)), so the second blank is \( y = kx \). The constant \( k \) is called the "constant of proportionality".

Answer:

First blank: varies directly; Second blank: \( y = kx \); Third blank: constant of proportionality