Side of the equilateral triangle = 3.5 cm
Area of the base = √34×(3.5)2
Let the height of water displaced in the prism = h cm.
Volume of solid cube = Volume of water displaced in the prism
⇒2×2×2 = √34×(3.5)2×h
⇒h=2×2×2×4√3×3.5×3.5
⇒h=1.5 cm
Since the water level rises by 1.5 cm, the new heieght = 10+1.5=11.5 cm
So, new height is 11.5 cm.