Mr.Li had a big rectangular styrofoam measuring 40cm by 40cm by 30cm. He cut cubes of side 4cm from it. What was the maximum number of cubes he could cut from the rectangular styrofoam?

30 does not divide evenly by 4, so we have to go down to 28 cm

if the block were 40 by 40 by 28
the number of blocks would be 10 * 10 * 7 = 70