The task of the snail

In this topic, I offer 3 fairly basic tasks for ingenuity. For novice programmers (probably for very beginners, a la school, because for a real programmer is too trite). Or, perhaps, for an interview, but to check specifically one narrow aspect: how much a person can make decisions at all independently, and not to bother and correct them.

Base

As a base, a fairly well-known snail problem for junior school was chosen. “A snail crawls up a 5-meter high pole. Every day she crawls up to 3 meters, and every night she slides down 2 meters. For how many days it crawls to the top of the pillar. "

As you know, many schoolchildren are cut off by the fact that they simply divide 5 by (3–2) and get 5 days, not taking into account that at the end of the third day the snail has already reached the top.

Task 1

Real non-negative numbers are entered: how many creeps up in a day; how much slides down for the night; post height. The answer should be displayed - the minimum necessary integer number of days.
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¹ By valid I meant floating point. You can take the whole. The bottom line is that, in general, the difference between the height of the pillar and the daily run may not be a multiple of the run for the whole day.
² These options, so be it, can be forgiven (or set in the condition that this will not happen).

The bottom line is that the decisive handles at least: (1) the classic case (the vertex is not reached on the first day, but exactly at the end of one of the days); (2) non-multiple length (the top is reached not on the first day and not exactly at the end of a certain day); (3) short length (the top is reached before the end of the first day).

Task 2

Same. Only it is necessary to return not the minimum necessary integer number of days, but “time” relative to the length of the day (possibly a non-integer number). It is assumed that every day and night lasts exactly 0.5 (and the process begins exactly at the beginning of the day). And the snail moves at a constant speed both during the day and at night.

Task 3

Same. Only the process starts at an arbitrary time, and not exactly at the beginning of the day. The user enters an arbitrary real number - the “time” of the beginning of the process. The answer is an arbitrary real number - the “time” of the end of the process.