Which is the direction of in stantaneous velocity for angular path

Right hand rule

Explanation:

The rule by which the direction of a rotational vector can be found: take your right hand, curl your fingers and stick your thumb straight up. If you let the curl of your fingers follow the path of the rotating particle or body, your thumb will point in the direction of the angular velocity of the body.

the old price per ounce is c/4.

the new price per ounce is c/3.6.

the ratio of the old price to the new one is

(c/4)/(c/3.6) = (c/c)×(3.6/4) = 0.9 . . = 9/10 . . "nine tenths" in either form