Mathematics Goes to the Movies

by Burkard Polster and Marty Ross

In the Navy (1941)

Smokey Adams (Bud Abbott) is a baker on a big battleship and his friend Pomeroy Watson (Lou Costello) a handyman.

1:06:04
Costello shows Abbott in three different ways that 7 times 13 equals 28.
ABBOTT: Hey, doghnuts!
COSTELLO: No, Smokey! Don’t!
ABBOTT: Oh, come on. One doughnut.
COSTELLO: I haven’t got enough. I can’t afford it. I just baked 28 of these things. Well, after all there are 7 officers I’ve got to feed and I’ve just got enough to give them---13 apiece.
Abbot asks Costello to prove to him that 7 times thirteen is twenty-eight. Here is Costello’s argument (minus nonessential dialogue)

1st proof (by bogus division).
COSTELLO: There were 7 officers. There’s a 7. Now I’m going to divide to prove it to you. Now, 28 doughnuts. (writes 7 and 28 and a blackboard) Now, 7 into 2. You couldn’t even push that big 7 into that little 2. Therefore we can’t use the 2. I’m gonna let Dizzi hold it. … I’ll use it later. Now, 7 into 8…. One (writes down a 1). …
Now, we’re gonna carry the 7. It’s getting’ a little heavy, so I’ll put it right down there.
7 from eight. … 1.
Now, a minute ago, we didn’t use the 2. I’m gonna use it now. Dizzy, give me back the 2. Thanks. Put it right down there.
Now 7 into 21?
ABBOTT: Three times.
COSTELLO: 7…. 28… 13.
ABBOTT: Now wait a minute!

2nd way (by bogus multiplication).
ABBOTT: Put down 13 up there. Now you claim that each officer gets 13 doughnuts? Put down 7, draw a line. Now 7 times 13 is what?
COSTELLO: 28
ABBOTT: Prove it.
COSTELLO: 7 times 3?
ABBOTT: 21.
COSTELLO: 7 times 1
ABBOTT: 7
COSTELLO: 7 and 1?
ABBOTT: 1.
COSTELLO: Two.
ABBOTT: Two.
ABBOTT: Oh no. Come on.

3rd way
ABBOTT: We add this up. Put down 13 seven times.
Now we’re getting it. You claim all this added up amounts to what?
COSTELLO: 28.
ABBOTT: Adding up the 3s from the bottom to the top: 3, 6, 9, 12, 15, 18, 21
COSTELLO: Just keeps adding the 7 1s from the top to the bottom: 22, 23, 24, 25, 26, 27, 28!