Chayei Sarah- Currency related activity ideas

A note to readers- Having written a full cycle of parsha posts, I've decided to try a slightly different approach. For this next cycle, I'm beginning with identifying a concept and then posing concept specific questions and activities for investigating the concepts at varying academic levels- still K-8 level.  I'd love feedback from readers as I keep the process going. Are you just an interested reader? Am I still keeping you interested? Are you a teacher/parent looking for ideas? Which ideas do you find most helpful? Have you tested out any ideas with your students/children? Looking forward to your feedback!
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"...And Ephron replied to Abraham, saying to him: 'My lord, hear me! Land worth four hundred silver shekalim; between me and you- what is it? And bury your dead.' Avraham listened to Ephron, and Avraham weighed out to Ephron the money that he had mentioned in the hearing of the children of Heth, four hundred silver shekalim in negotiable currency. And Ephron's field, that was in Machpelah, that was facing Mamre stood- the field and the cave within it and all the trees in the field, within its entire boundary all around- as Avraham's as a purchase in the view of the children of Heth, with all who came to the gate of his city. And after that, Avraham buried Sarah his wife in the cave of the field of Machpelah facing Mamre, which is Hevron, in the land of Canaan." ~Bereishit 23;14-19

Activity Connections:
The two ideas that stand out to me from this passage are:
1) Avraham's weighing out of the money
2) The fact that the Torah specifically says that he was using "negotiable currency"

For some previous thoughts about scales and balance, see my post on Parshat Ki Teitzei where I talk about weights and measures.

Rashi on 23;16 explains that "negotiable currency" is stated because the shekel that the Torah usually refers to is a smaller shekel (equal to 1 sela). In our case, though, Avraham chose to use shekels which are acceptable as currency even in areas that use larger shekels ("kanterin", which are equal to 100 selas). 

Activity ideas in increasing conceptual difficulty:
*Discussion and exposure to local current-day currency; discussion around equivalent currencies
eg. for US currency, exposure to pennies, nickels, dimes, quarters, half-dollars, dollar coins, dollar bills, etc and discussion/practice with the value of each and equivalencies (5 pennies = 1 nickel; 25 pennies = 1 quarter = 5 nickels = 2 dimes + 1 nickel)

*Combine currency with the idea that Avraham weighed out his money. Does this still work with current day currency? Will 5 pennies balance with 1 nickel on a balance scale? Our current money is more of a representation of value than true equivalence between coin sizes, weights, and values.

*Look at the difference between what 400 shekalim would have been if they were each 1 sela instead of being 1 kanterin. This can be done at varying levels for different ages and abilities. What does it physically look like using manipulatives to represent 1 sela? How could you calculate how many selas Avraham actually paid Ephron? 

*If you look at the comments section in last year's post on Chayei Sarah, you'll find a link to some calculations on current day equivalence for a shekel (one that's the value of a sela). How can you use this information to calculate the current day value for what Avraham actually paid for Maarat HaMachpelah? How different is that from what he would have paid in current day currency if he used selas instead of kanterin?

*How does the amount of money paid toward Maarat HaMachpelah compare to the value of Rivkah's dowry (the bracelets and nosering discussed in last year's post)? How does a beka compare to a sela? to kanterin?

*If you compare the difference between values of selas and kanterin, is the difference linear growth or exponential growth? (Hint: 1 kanterin = 100 selas; 2 kanterin = 200 selas; and so on)

Chayei Sarah - Unit Conversion

"And it was, when the camels had finished drinking, the man took a golden nose ring, its weight a beka, and two bracelets on her arms, ten gold shekels their weight." ~Bereishit 24;22

Unit Conversion:

Unit (or Unit of Measure): a standard amount of a physical quantity (ref. dictionary.com)

In Math and Science, units are a critical aspect of calculation. Units, in simple terms, are the base quantity that we choose to use to measure physical properties- a length, a weight, a volume, etc. You can measure with standard units- units that are already established by society and have specific value assigned to them (e.g inch, cm, pound, gram, gallon, liter, etc.); You can also measure with non-standard units- units that you choose for you convenience, but are not standardized to all places and situations (e.g. the paperclips that I have in a box on my desk, or the length of my right foot).

In order to compare measurements of different items, we need to measure them using the same units. This is where unit conversion comes in. If we have items measured in different units, then we need to convert them all to the same units of measure in order to be able to say how they compare to each other. We need to know how many cm are in an inch, and then make sure that all items we're comparing are measured in either cm or inches. In general, it doesn't matter which measure you choose to use, you just need to pick one and make sure that everything that you're comparing is measured with the same measure. If I want to compare my height over the past 5 years, I can measure myself consistently in ft, or I can have some measurements in ft and some in meters, but in order to compare, I need to convert all the measures to either ft or meters to know how my height has changed. Note that in order to calculate the conversion from ft to meters or vice versa, I need to know that 1 meter is approximately 3.28 ft.

So, how does this connect to the parsha?

In Chayei Sarah (Bereishit 24), Avraham's servant, Eliezer, is sent to find a wife for Yitzchak. When Rivkah meets him at the well in Nahor and she offers water to both him and his camels, he realizes that she is the right woman for Yitzchak. He then, in Bereishit 24:22, gives a gift to her-- and here is where we find units of measure. Eliezer gives her "...a golden nose ring, its weight a beka, and two bracelets on her arms, ten gold shekels their weight."

So, what if we want to know how much the weight of her jewelry was altogether? Or, how big was the nose ring compared to the bracelets? How can we compare the weight of a beka and the weight of ten shekels? Rashi helps us out here and tells us that a beka is the weight of a half-shekel (see Rashi on this Pasuk to see how he knows this). So, we now we know that the nose ring was the weight of a half-shekel and the two bracelets were the weight of 10 shekels. So, the weight of all of Rivkah's jewelry from Eliezer was 10.5 shekels. The weight of the two bracelets together was 20 times the weight of the nose ring. Or, if we assume that the bracelets were equal in weight, then each bracelet was 10 times the weight of the nose ring.