(2) When the iron bar rises, the water also falls, and the rising volume of the iron bar is equal to the falling volume of the water.

Suppose the water drops by x centimeters,

Rising volume of iron bar = 15× 15×24=5400,

The falling volume of water =60×60× x,

That is, the equation 60×60× x=5400 is obtained.

X = 1.5cm，

As the title says, the original iron bar was immersed in water 1-0.5=0.5 m =50 cm.

Soak the iron bar in water for 50-24- 1.5 = 24.5cm after rising.

Ask again if you don't understand. I wish you progress in your study and go up a storey still higher! (*^__^*)