A plaque remaining from the Big Apple Night Club at West 135th Street and Seventh Avenue in Harlem.

Above, a 1934 plaque from the Big Apple Night Club at West 135th Street and Seventh Avenue in Harlem. Discarded as trash in 2006. Now a Popeye's fast food restaurant on Google Maps.

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Entry from July 14, 2020
“5Q + 5Q = ?"/ “10Q."/ “You’re welcome.”

A old math joke is:

“5Q + 5Q = ?”
“You’re welcome.”

“10Q” sounds like “thank you.” The joke has been cited in print since at least the 1920s.

Google Books
The Cornell Civil Engineer
Volumes 37-38
Pg. 196:
C.E. ‘31— “By the way, you think you know your calculus. Then what is 5Q plus 5Q?”
C.E. ‘32— “10Q, of course.”
C.E. ‘31— “You’re welcome.”

25 September 1933, Birmingham (AL) News, “The Coal Bin” by Henry Vance, pg. 8, col. 6:
“What’s 5Q and 5Q?” Your fall guy answers, “10Q,” whereupon your answer is, “You’re welcome.”

Google Books
January 1937, Boys’ Life, “Think and Grin” edited by Frank J. Rigney, pg. 23, col. 1:
Soph: How much is 5q plus 5q?
Fresh: Ten q.
Soph: You’re welcome.

Google Books
July 1973, Boys’ Life, “Think and Grin,” pg. 66, col. 2:
Willy: What’s 5Q plus 5Q?
Nilly: Uh— 10Q.
Willy: You’re welcome! — John Garcia, South El Monte, Calif.

Google Groups: comp.windows.ms
Broken Window
Bob N Keenan
~ Bob N. Keenan | ALGEBRA QUIZ
~ University of Wisconsin-Milwaukee | Q: What is 5q+5q?
~ | A: You’re welcome!

Google Groups: mpc.lists.misc.giggles
JOKE-CLEAN: Answering Machine Messages
Brian Myers
13.  Please leave your name and number—But first, a short algebra quiz: How much is 5Q + 5Q? (Pause while caller thinks: 10Q) You’re welcome!

alyssa lovato
What’s 5Q+5Q?......10Q....."You’re welcome” Hahahaha
1:21 PM · Jun 14, 2009·Twitter Web Client

What’s 5Q+5Q?
...you’re welcome.
2:49 PM · Aug 10, 2014·Twitter for Android

Posted by u/ThreadlessJon August 15, 2015
A math teacher ask his students, “What is 5Q + 5Q?”
The class responds, “10Q.”
The teacher responds, “You’re welcome/”
Whats 2Q + 2Q?

Posted by u/justinsjams April 28, 2019
Whats 5Q + 5Q?
You’re welcome.

Tom Osborn, PhD, FRSA.
Dad/Maths joke. It’s been a while, so here…
5Q + 5Q = ?
You’re welcome.
11:39 PM · Jul 13, 2020·Twitter Web App

Posted by u/lone_wolfenstein July 13, 2020
5Q + 5Q = ?
You’re welcome

Posted by Barry Popik
New York CityEducation/Schools • Tuesday, July 14, 2020 • Permalink