Fill in the blank with either “directly” or “inversely”.

(1) Area of an equilateral triangle: A=(√3s^{2})/4

A is proportional to s.

(2) Average speed: r=d/t

R is proportional to t.

(3) Surface area of a sphere: S=4πr^{2}

S is proportional to r.

(4) Free vibrations:

is proportional to W.

(1) The constant is multiplied to s^{2} to yield A; √3/4 = k → directly

(2) The constant divided by t yields average speed; d=k → inversely

(3) The constant is multiplied to r^{2} to yield S; 4π = k → directly

(4) The constant divided by W yields ; =k → inversely