OlympiadMediumLogic5–6

A snail at the bottom of a well $10$ m deep climbs $3$ m each day and slides back $2$ m each night. On which day does it first reach the top?

Um caracol no fundo de um poço com $10$ m de profundidade sobe $3$ m por dia e escorrega $2$ m por noite. Em que dia chega ao cimo pela primeira vez?

Answer options

Solution

Each full day-and-night gains $1$ m, but on the last day there is no slide back. The snail needs to reach $10 - 3 = 7$ m by nightfall, which takes $7$ days, and climbs out on day $8$ .

A snail at the bottom of a well 101010 m deep climbs 333 m each day and slides back 222 m each night. On which day does it first reach the top?

Answer options

A snail at the bottom of a well $10$ m deep climbs $3$ m each day and slides back $2$ m each night. On which day does it first reach the top?