This rectangular tank...

Question

This rectangular tank is partially filled with water. When a brick measuring 20 cm x 20 cm x 10 cm is placed in the tank the water level reaches the brim. How many liters of water are there in the tank before the brick was put in? (Tank: h-39 cm, l-1/2cm, w-40 cm) 

Answer 1

Perhaps the problem should have said: "1/2 meter," then

“partially full” + brick = full

“partially full” + (20 cm * 20 cm * 20 cm)  = 39 cm * 0.5 m * 40 cm

"partially full" + (20 cm * 20 cm * 20 cm)  = 39 cm * 50 cm * 40 cm

“partially full” + 8000 cm^3  =  78000 cm^3“

partially full”  = 70000 cm^3

    ( Now, convert:   1000 cm^3 = 1 liter )

 

"partially full" = 70 liters