Yeah, this one doesn't have anything to do with math, does it?

Off the top of my head, I'd guess that tides lose about an hour per day, so the tide would be in at 1:00 pm.

Ah, I guess the point of this is that the next tide is half way between those two, and so would be just after midnight.

But to know this, you'd have to know that the tide's cycle is slightly longer than the day's cycle.

Considering the moon was at its highest today at 12:00, and will be at its highest again in ~29 days at 12:00, what time will the moon be at its highest tomorrow, which is 1/29 of its cycle?

The question then turns into dividing 24 hours into 29 parts, or about 48 minutes per day, so 12:48.

Bonus points (not in math) go to whoever knows that a tide can also come when the moon is at its lowest, or half that time, or 0:24 or so.

It wouldn't be a Russian textbook without some completely unreasonable problems.

At 1pm, considering that tides usually go with 6 hours and 15 minutes increments?

(I hope my memory is right, took the RYA exam a while ago)