Question 1205079
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Floor area = length*width 
= 9*7 
= 63 cm^2


Volume of water = (floor area)*height
= 63*4
= 252 cm^3


Or we could say it like this
Volume of water = length*width*height 
= 9*7*4 
= 252 cm^3


When placing the cylinder onto its circular end, the floor area will shrink. 
It goes from 63 cm^2 to (63-9pi) cm^2
The 9pi is the area of the circle of radius 3 cm (i.e. diameter 6 cm).


h = new height


The old volume of water (252) will not change. This assumes the water doesn't spill of course. 


old volume = 252
new volume = (new floor area)*(new height)
new volume = (63-9pi)*(h)
new volume = 252


(63-9pi)*(h) = 252
h = 252/(63-9pi)
h = 7.25688023221569
I used my calculator's stored version of pi to get the best accuracy possible. 


If we rounded to let's say 4 decimal places, then the height is roughly h = 7.2569 cm
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