Posted by: R Jonathan Gewirtz | August 22, 2018

Do the Math


My grandfather used to be a bookkeeper and he used to always tell my mother to do math in her head, not using a calculator, which is something that she used to say to me.  I hated it but followed her lead, and now I do math in my head, and it comes in handy all the time.   I tell it to my kids also, and they roll their eyes, but when they can figure out the change in the supermarket faster than the cashier who’s using the register, even they have to admit it’s pretty cool.

I know, some people say, “Aha! Another day gone and I didn’t use Algebra,” but I think some types of math are really important.  When my mom wanted to buy something but thought it was too expensive, my father would put it in perspective.  Let’s say it was a $900 refrigerator.  My dad would say, “If it lasts ten years, that’s ninety dollars a year, less than two dollars a week, it’s like a quarter a day.  That’s not a lot of money to have fresh food.”

I used a similar rationale when I did the cost-benefit analysis for putting a back-up generator in my home.  If my freezer defrosts and I lose a couple hundred dollars of food, that’s money saved right there by preventing a meltdown.  And, of course, there are other types of meltdowns possible.  I won’t cast aspersions at my wonderful wife and children but let’s just say that the stress of being without power can be pretty difficult.  With an extended power outage, the necessary follow-up therapy alone would cost more than the generator!  Doing the math helped make the decision easier.

There are other ways we can do the math.  If you need gas and one place is close but is more expensive than the farther station, figure out how many gallons you need now, and the price difference.  See if it is worth your time.  If you’re getting ten gallons at twenty cents more than you might have paid, decide if your time and inconvenience (not to mention extra mileage) is worth more than two dollars.

If you can do a favor for someone, figure out how much it will cost you (an extra five minutes?  Two minutes?) and weigh that against how much it will help them or make them feel good.  If you make someone’s day, to quote my wife’s grandfather, “Could you buy that for money?”

Of course, as I’m required by contract to mention shopping carts at regular intervals, figure out how long it will take you to push the wagon the extra fifteen feet before you get into your car and compare that to how long it will take someone else who wants to park in that spot to get out of their car, move it, and get back into their car before they can do so.  It’s at least four to five times longer for the next person, so who but a creep would put them through that?

You can take that to all different scenarios as long as you remember that everyone has a common denominator: time stops for no man.  If I can transform my time into a mitzvah because I’m saving someone else time, I’ve put it to a better use than I probably will if I’m callous towards others.  And there’s more.

A friend of mine suggested that I upload my weekly Parsha sheet to a certain website in Israel that hosts hundreds of Diveri Torah sheets.  I actually had a fellow who lives near me ask to be on my mailing list (as can any of my readers, e-mail me at and put Subscribe in the subject) because he saw it there.  That man sends out Divrei Torah, so who know how many more people are reading it now.  But distributors aside, according to the site, since my friend recommended it a year ago, I’ve gotten over 2500 downloads.  With an average of 1,000 words per sheet, that’s over TWO AND A HALF MILLION words of Torah, (each word being greater than all the other mitzvos) which my friend gets credit for simply from giving someone an idea.  If you do the math, you’ll see how quickly things add up!

[Since this was originally published, the downloads have risen to 12,964 or nearly THIRTEEN MILLION words of Torah and still going.]

In life, we are supposed to make a cheshbon hanefesh, a reckoning of our souls.  We’re supposed to weigh the benefit of a sin against how much we will lose by committing it, and the relatively cheap cost of a mitzvah against the incalculable reward we will get for it.  Who knew that such a cheshbon could include actual arithmetic?  I sure didn’t, but it works, because when you put the facts on the table, the answers are simple and clear.

You can put the calculator on the shelf because these calculations must be done in your head and heart, and I guess that about sums it up.


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