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9
votes
1answer
149 views

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 ...
0
votes
0answers
22 views

Trying to get Shmita year dates without a headache [duplicate]

I would like to know the shmita dates starting from 5775-5733. example:5775 (25 Sept 2014 - 13 Sept 2015)
4
votes
0answers
82 views

Slide Rule on Shabbos/Yom Tov

May a slide rule (mechanical device before calculators) can be used on Shabbos for Gemara calculations?
5
votes
1answer
69 views

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 ...
6
votes
1answer
153 views

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 ...
4
votes
1answer
122 views

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 = ...
3
votes
1answer
66 views

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 ...
2
votes
1answer
58 views

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 ...
4
votes
1answer
236 views

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 ...
4
votes
1answer
130 views

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 ...
13
votes
5answers
841 views

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 ...
0
votes
1answer
160 views

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 ...
2
votes
0answers
115 views

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 ...
7
votes
4answers
396 views

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? ...
2
votes
2answers
174 views

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 ...
5
votes
3answers
235 views

Mathematics in Cheder

I recall reading that their is a pesak/teshuvah/report by a major posek, perhaps an early "later" Acharon, (Rabbi Akiva Eiger zt"l) which noted that at least elementary arithmatic or mathematics was ...
8
votes
2answers
480 views

Magen Avraham - Practically no Plag HaMinḥah or just no Plag HaMinḥah in winter?

Calling all science and math-oriented Judaism.SE-ers! According to the website MyZmanim.com, today's Halachic times where I work are as follows (only a handful of times are shown because the question ...
7
votes
1answer
326 views

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)?
5
votes
1answer
244 views

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. ...
11
votes
2answers
583 views

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 ...