During the day, the snail will climb the pillar by 4m, during the night – it will descend by 3m.

During the day, the snail will climb the pillar by 4m, during the night – it will descend by 3m. On Monday, the snail began its ascent from the foot of a 10-meter pillar. What day of the week will she get to the top of the pillar?

Since during the day the snail rises up the pillar by 4 meters, and during the night it descends by 3 meters, its daily movement is 4 – 5 = 1 (meter). On Monday, the snail began its ascent from the foot of the ten-meter pillar. In six full days, it will reach a height of 6 meters. On the seventh day, the snail will climb the pillar by another 4 meters and will be at a height of 6 + 4 = 10 (meters). This will happen next Monday.
Answer: next Monday the snail will reach the top of the ten-meter pillar.