# Tagged Questions

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### Mikvah Math for the Sea of Shlomo

In calculating the number of Mikvas that the "Sea of Shlomo" could hold, the Gemara (Eruvin 14b) calculates that it would hold 150. The Gemara asks, that being that the Sea was round, and the area/...
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### High School Math in the Talmud

I'm currently tutoring someone in math that has an atitude of "what's the point of all this... why would I ever need this..." (which is typical of many high-schoolers). To try to pique his interest, I ...
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### Card Counting Permissibility

For what it is (if you haven't heard of it), see Card Counting (wikipedia) Also assuming Gambling is not a problem in that scenario. It's perfectly legal in the U.S. So would it be a problem in ...
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### How complicated can a vesst pattern be?

Background: In the laws of niddah there is something called a vesst haflaga, which is a period that occurs at some consistent interval. If a woman establishes a pattern for some amount of consecutive ...
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### Rolling dice on shabbat?

I was told that when rolling dice [for a game, such as backgammon] on shabbos one should roll one di, move the pieces, and then roll the other di [and move the pieces]. The reason for this, I was told,...
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### Game theory in the Tanaim

I read an article a while back (maybe over a year ago?) in the Mishpacha English Magazine (I'm pretty sure, although it may have been in the Ami) that discussed a certain machlokes Tanaim about how to ...
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### What is the hallachic definition of randomness?

A new Shabbat-friendly technology, KosherSwitch, uses randomly timed light pulses to create various safeks, so that flipping the switch does not hallachically count as switching the light on, even in ...
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### Why do all of them say that there were 5 times more plagues at the sea, instead of 1.5 times?

In the Haggadah it says: (text from WikiSource) רַבִּי יוֹסֵי הַגְּלִילִי אוֹמֵר: מִנַּיִן אַתָּה אוֹמֵר שֶׁלָּקוּ הַמִּצְרִים בְּמִצְרַיִם עֶשֶׂר מַכּוֹת וְעַל הַיָּם לָקוּ חֲמִשִּׁים מַכּוֹת? ...
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### If the Torah tells you not to add or subtract, what does it imply for behaviour?

If the Torah forbids addition and subtraction, what does it imply for Jews, and for ultra orthodox jews, regarding practical life? It is a baffling rule. Can you you use money at all? can you not ...
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### How does this math work out?

The Gemara Eiruvin 56b said that the Migrash (the orange area) is one quarter of the area of the sados (the green area). Let's look at the math. (This is how I understood the maskana) greenArea = (...
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### Is the passage describing an approximation of pi or is it one of the miracles of Bais Hamikdash?

In Sepher M'lakhim we read how different measurement was taken. I wonder if this passage (Ⅰ M'lakhim 7:23) is describing an approximation of PI (3.1415...), or was this one of the hidden miracles? ...
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### Today is the square-root of 25th day of the omer

If you haven't counted sefirat haomer yet that night, you're not supposed to say the current day (for example, 'today is the 5th day') before making the bracha. But what about saying what today is in ...
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### Pidyon HaBen rate

About how many pidyon haben ceremonies are required to be performed per 1000 Jewish births in the past few decades? The requirements for a pidyon haben are: Both parents are Israel, not Kohen or ...
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### Slide Rule on Shabbos/Yom Tov

May a slide rule (mechanical device before calculators) can be used on Shabbos for Gemara calculations?
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### What is considered a Safek?

I've been learning all these laws about Sekefot-doubts, but I'm coming up shy on a basic point. What is considered a Safek? Example:if there are 100 pieces of lettuce and I check all of them and only ...
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### How big does a pentagonal Sukkah have to be?

What is the minimum length requirement for each of the walls of a 5-sided sukkah? What about 6 sides? What about 7? ... What about ∞ sides (i.e. a circle)?
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### Aruch Hashulchan's moon-distance estimate

Aruch Hashulchan, Orach Chayim 397:1, says that a מיל is the same as a Russian верста (verst) or 500 сажен (sazhen), which comes to 1066.8 meters. In 426:2, he says the distance to the moon is about ...
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### What does ריש חזית mean?

I'm reading(/trying to read) the introduction to the Vilna Gaon's איל משולש (his geometry textbook). The first two words are ריש חזית. What does ריש חזית mean? If it helps, the phrase is immediately ...
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### How many calories are in a KeZayith of flour?

I've often wondered how I can be sure I've eaten a KeZayith of flour when I eat something small but complete - like one cookie - and struggle with the decision of whether or not to eat more in order ...
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### Rambam's method for calculating the conjunction of the moon (and sun)

I think I'm missing something basic here... The Rambam, in Hilchot Kiddush Hachodesh (6:3) says that the interval between one conjunction to the next is is 29 full days, 12 hours of the 30th day, and ...
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### An improved Jewish calendar after this one expires?

Conventional wisdom has it that about 1600 years ago, the latter Hillel utilized his Sanhedrin to sanctify the Hebrew calendar as we know it today until the year 6000. (Presumably by that point we'll ...
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### Origins of איל משולש and Vilna Ga'on's bathroom math

There is a well-known fact that the Vilna Ga'on studied math while in the bathroom since Torah was out of the question in an unclean place. It is also somewhat well-known that he produced the material ...
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### Do we know anything else about the calculus problem solved by Rabbi Moshe Feinstein?

The biographical sketch of Rabbi Moshe Feinstein that appears in Igrot Moshe volume 8 describes the following (my translation): The Communist takeover meant the schools taught against religion. ...
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### How to calculate 60 days from tekufat tishri for any given year?

I'm trying to pin down an algorithm for calculating when to start saying ותן טל ומטר in diaspora. (In Israel it begins 7 Cheshvan.) I've gotten that we need to know how many centuries passed since ...