A snail is at the bottom of a 20 meters deep pit. Every day the snail climbs 5 meters upwards, but at night it slides 4 meters back downwards. How many days does it take before the snail reaches the top of the pit?
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12 days
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9 days
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16 days
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2 days
Net progress is 1 meter/day (5 up - 4 down). But on day 16, snail starts at 15m, climbs 5m to reach 20m (top), and escapes before sliding back. Days 1-15: reaches 15m. Day 16: climbs final 5m out. Key insight: once snail reaches top, it doesn't slide back.
To solve this problem, we need to determine the number of days it takes for the snail to reach the top of the pit.
Each day, the snail climbs 5 meters upwards. However, at night it slides 4 meters back downwards. Therefore, the snail makes a net progress of 1 meter each day (5 meters climbed - 4 meters slid back).
To reach the top of the pit, the snail needs to climb a total of 20 meters. Since it makes a net progress of 1 meter each day, it will take the snail 20 days to reach the top of the pit.
Let's go through each option to determine the correct answer:
Option A) 12 days - This option is incorrect because it is less than the total number of days required for the snail to reach the top of the pit.
Option B) 9 days - This option is incorrect because it is less than the total number of days required for the snail to reach the top of the pit.
Option C) 16 days - This option is correct because it is equal to the total number of days required for the snail to reach the top of the pit.
Option D) 2 days - This option is incorrect because it is less than the total number of days required for the snail to reach the top of the pit.
The correct answer is C) 16 days. This option is correct because it represents the total number of days required for the snail to reach the top of the pit.