(15×8×8)÷320=960÷320=3 (cm)
Answer: If the iron block is placed horizontally in the water, the water will completely submerge the iron block and the water surface will rise by 3 cm.
[2] Because iron is not completely submerged by water, it is difficult to calculate, so we should use the method of solving equations to calculate:
Analysis: ① The bottom area of container should be =320- the bottom area of iron block =320-8×8=256 cm2.
(2) The immersion height of iron in water = original height of water surface+rising height of water surface =8+ rising height of water surface.
Assumption: the water surface rises by x cm;
Column equation: 8× 8× (8+x) = (320-8× 8) x.
Solution: 5 12+64X=256X.
5 12=256X-64X
192X=5 12
X≈2.6666667 cm
Answer: If the iron block is placed vertically in the water, the water level will rise by 2.67 cm.