A2.0-cm-thick bar of soap is floating on a water surface
sothat 1.5 cm of the bar is underwater. bath oil of specific
gravity0.60 is poured into the water and floats on top of the
water. whatis the depth of the oil layer when the top of the soap
is justlevel with upper surface of the oil?

Explanation:

Given

thickness of soap bar t=2 cm

thickness underwater t'=1.5 cm

oil is poured in the water with specific gravity=0.6

Soap top surface is just level  with the upper surface of oil i.e.

weight of soap is balance by buoyancy effect of oil and water

initially soap is balanced by water

if

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