The holiday of Pesach Sheini occurs this Monday. It is an amazing concept: Jews in the desert felt left out for missing the Pesach offering. They pleaded with Moshe and Hashem to be given another opportunity. They were granted their wish. They were given the holiday of Pesach Sheini on the 14th of Iyar, 30 days after Pesach.

These Jews got a second opportunity after 30 days. What if it were the other way around? That is, what if the number of Pesach Sheini sacrifices doubled each day for 30 days straight? That would mean two offerings on the first day after Pesach, four on the second day, eight on the third day, and so on. Let’s call this imaginary situation Pesach 2.0. How many Pesach 2.0 offerings would be brought on the 30th day?

This problem requires multiplying 2 times itself 30 times. It’s almost impossible to do this by hand. Here’s a mental math trick to get a good estimate: Whenever we multiply a number repeatedly, we can break the problem into groups. For example, suppose you want to multiply 2 times itself 6 times. You can break the 6 into two groups of three. Now 2 x 2 x 2 = 8. We then multiply the two groups together to get 8 x 8 = 64. This is easier than multiplying 2 by itself 6 times.

We can use the same trick for 2 times itself 30 times. If we multiply 2 times itself 10 times, we get a number close to 1,000 (1,024 to be exact). Do you see how to estimate 2 times itself 30 times?

Once you calculate that number, compare it to the original Pesach Sheini. The Pesach Sheini sacrifice was offered only once on the 30th day. How frequently would you bring the Pesach 2.0 offerings throughout the 30th day? (Hint, there are 86,400,000,000 microseconds in a day.) Would you need to work faster than a modern day computer? They do about 2 billion calculations per second. That’s 2,000 calculations each microsecond.

Solution: We need to calculate 2 times itself 30 times. We can use the mental math trick. Break the whole set of 30 into three groups of 10. Each of those groups equals about 1,000. Multiply 1,000 times itself three times and we get 1,000,000,000. That’s 1 billion. (The exact answer is closer to 1.07 billion.)

This means, you would need to bring a Pesach 2.0 sacrifice every 86 microseconds on the 30th day. That’s not as fast as a modern computer. They do a calculation about once every 0.0005 microseconds. However, it’s still pretty fast. Shabbat Shalom.

Ari Blinder is a math educator living in Highland Park. He is the owner of Math for the Masses, an innovative tutoring and consulting company. Please visit www.math4masses.com for fun activities and helpful worksheets. Ari can be reached at [email protected]. Never think you are “not a math person.” You are very much one already, but no one has shown you how.