Several planks measuring 4 cm × 30 cm × 50 cm were sawed off from a wooden block measuring 30 cm × 50 cm × 90 cm.

Several planks measuring 4 cm × 30 cm × 50 cm were sawed off from a wooden block measuring 30 cm × 50 cm × 90 cm. After that, a block with a volume of less than 4000 cm3 remained. How many boards have you sawed off?

1) 30 * 50 * 90 = 135000 (cm ^ 3) -the volume of a wooden block
2) 135000-4000 = 131000 (cm ^ 3) -the volume of the sawn-off part
3) 4 * 30 * 50 = 6000 (cm ^ 3) – the volume of one plank
4) 131000: 6000 ~ 21 (pcs) -maximum value of sawn planks
Answer: 21 or less