Which would show an example of how physical changes are reversible? cutting a gold bar in two pieces and then putting the pieces next to each otherburning a match and then relighting itmelting tin and then cooling it into a moldcombining sodium and chlorine to make the new material of table salt?

Melting tin and cooling it into a mold.

Explanation:

Physical changes are those that keep unvariable the internal structure of the materials, chemical changes, instead, are those that modify their composition.

That's why we say that physical changes are reversible, and chemical ones are irreversible.

Among the options, we can see two physical changes (those which involve gold and tin) and two chemical changes (those which involve a burning match and sodium and chlorine).

Among the two physical changes, only one shows its reversibility, that is the tin experiment.

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

answer(20) psi;