 JEWISH MATH  Email us: editor@OhrShlomo.com

Welcome to Jewish math. So what can be "Jewish" about math? Well, in fact, math can be very Jewish, but it just depends on how you apply it, as we do here. So follow along, learn and enjoy the few Jewish math problems and examples that follow:

Hebrew alphabet - אלף בית:

Alef Bais number matching:

Did you know that the Hebrew אלף בית has a unique number that matches each letter? For sure! Take the first letter, א, for example; guess what number matches it? The matching number is one “1.” So, for ב, the matching number would be “2,” for ג it is “3,” and so on. You can even do arithmetic with them; just as 1 + 1 = 2, 1 + 2 = 3 and 2 + 2 = 4, so, likewise, does:
א + א = ב ,א + ב = ג ,ב + ב = ד.

Here is the list of matching numbers as follows:

How do you do a number like 12? Simple, י + ב, which is the same as 2 + 10 equals 12 (or יב). Likewise, 18 = י + ח (or just יח).

Be careful, though. We don’t write ה and י next to each other, and the same goes for ה and ו, because these are names of Hashem. We are forbidden to use these except when davening or the like. So, for 15 use טו, which is (6 + 9 = 15), and for 16 use טז.

Exercises (click on the right answer):

1.) What are the matching letters for 25 ?
2.) Which letters match 15 ?
3.) What number matches נז ?
4.) What is ג + ד ?

Elementary level:

Fill in:

1.

Mommy bought 4 eggs יום ראשון and 3 eggs יום ששי. How many eggs did she buy for that week?

2.

What number is קר ?

Read each sentence. Click on the picture that best describes the sentence.

1.)Which is the largest of these?

2.) Which is the longest Mezuzah?

3.) Which is the biggest Sukkah?

4.) The smallest letter?

5.) What is the shortest dreidel?

A Mitzvah Tank is cruising along, bringing Chassidim to see the Rebbe. They started out from Miami at 10:00 AM and arrived in New York at 6:00 AM, the next day. On the first half-duration of the trip, they averaged 70mph. On the second half-duration (this includes the night and rest stops, they averaged 80 mph. During the night, the drivers observed a life-saving directive of the Rebbe, in order to prevent an accident, ח״ו. They stopped every hour to walk around a little in fresh air, relax and rest. These rest stops totaled one hour. An additional stop, for 20 minutes, was to put tefillin on a couple of Jewish travelers, they made contact with on their citizens band radio.

What was the total distance traveled? Select best answer.

Solution: First let's get the time on the road for each half:

Total time = 20 hours
First half   = 10 hours
Total stops = rest stops (1hr) + tefillin (20 min) = 1 hr 20 min
Second half = 8 2/3 hrs (10 hrs - total stops [1:20] )
Now, Rate x Time = Distance

Rate Time Distance
First
half:
70
mph
10
hours
½
d
Second
half:
80
mph
8 2/3
hours
½
d

D = 70 m/hr x 10 hr + 80m/hr x 8 2/3 hr = 700 miles + 693.33 miles = 1,393.33, miles total

In preparation for a Daf Yomi Shiur, Rav Weiss and Rav Schwartz worked on typing, editing and printing learning material for a large attendance. If Rav Weiss can do the job by himself in 2 hours, and Rav Schwartz can do it alone in 3 hours, how long will it take the two of them together?.

Solution: Okay, it's like this: Rav Weiss can do 1/2 the work in 1 hour. Rav Schwartz, on the other hand, needs 3 hours to do the job. So, he does 1/3 the work in 1 hour. Together (let's call it "t"), they can do it in 1/t . So, let's set it up like this:

Rav Weiss = 12 per hour
Rav Schwartz = 13 per hour
t (together) = 1t

Now let's put it together -

12 hr + 13 hr = 1t
36 hr + 26 hr = 1t
56 hr = 1t
t = 65 hours

So, it takes 1 15 hours for the two of them together to complete the job.

A mobile mikva is filling up, partially with both: rain and ocean water. The rain water fills the mikva at the rate of 20 seahs per hour and the ocean water does this at the rate of 30 seahs per hour.

How long will it take for the mikva to fill to its capacity of 80 seahs? Select best answer

Solution: Just as rate x time = distance, so does rate x time = capacity.

Capacity = 80 seahs.
Ocean water rate = 30 seahs/hr.
Rain water rate = 20 seahs/hr.
hr = time it takes for both, the rain and salt water, to fill the mikvah to capacity.
So, 30 seahs/hr + 20 seahs/hr = 80 seahs, 50 seahs/hr = 80 seahs.
hr = 80 seahs/50 seahs = 1.6 hrs
Hence, it takes 1 hr and 36 minutes to fill the mikva to 80 seahs.

To be continued...