# 18 × 4 is not 72

According to most Poskim, it takes 18 minutes for an average person to walk a distance of one mil, and therefore 72 minutes to walk 4 milin.… Others say it takes 22.5 minutes to walk a mil, and therefore 90 minutes to walk 4 milin.

(Emphasis in the original.)

If it takes me 18 minutes to walk a distance, it's going to take me more than 72 minutes to walk four times that distance. People walk far distances more slowly than short distances as far as I can tell.

More extremely, I see the same proportion applied to four amos, which is even more unrealistic. Surely if it takes me 18 minutes to walk a mil (2000 amos), it doesn't take me 18 ÷ 500 minutes to walk four amos! I don't walk a mil at anywhere near the speed I walk four amos at!

Have any pos'kim dealt with the idea that those numbers don't match up?

Edit: Double AA pointed out in a comment that I'm asking this backward: the original source says it takes twelve hours to walk forty mil, and the other distance-time conversions are derived from that one. Either way, the question remains.

• My guess is that we have a fixed "standard walking speed", even though actual walking speeds vary. The same way we have a "standard olive" even though not all olives are the same size and a "standard amah" even though everyone's arms are different. – Heshy Sep 9 at 19:25
• @Heshy that's definitely how Rabbenu Tam et al take it, but I don't see why it has to be that way if you reject (with good reason) his whole zmanim worldview. For RT the Gemara in psachim is discussing Halakhic shkiya/tzeis, like the Gemara in Shabbat, and must be using an objective unit. If you reject that then the latter discusses Halakhic times and the former discusses traveling expectations. – Double AA Sep 9 at 19:45
• @DoubleAA it's still reasonable to have a standard approximate speed to use in calculations even though it's not exactly right. – Heshy Sep 9 at 20:22
• @Heshy only if there are calculations to do. Outside Rabbenu Tam world is there ever a need to calculate hillukh X mil from Y mil? (Even if you find some instance of Parsa let's say, there's no reason the times need to be proportional 1:4 like the distances are.) – Double AA Sep 9 at 20:23
• @doubleaa Rabbi Yehuda in Yoma 6:8 – Heshy Sep 10 at 10:23