“Why is 6 afraid of 7?”/“Because 7 8 9.”

A children’s number riddle is:
 
Q: Why is 6 afraid of 7?
A: Because 7 8 (ate) 9.

 
The joke has been cited in print since at least 1986. “Why is 6 afraid of 7? Because 7 is a registered 6 offender” is a related riddle.
 
“6 was afraid of 7 because 7, 8, 9, but why did 7 eat 9?”/“Because you’re supposed to eat 3 squared meals a day” is a joke based in this one.
   
   
19 January 1986, Chicago (IL) Tribune, “Orbiteers Message Center,” pg. G49, col. 7:
Why was 6 afraid of 7?
 
12 December 1987, The Times (Trenton, NJ), “Good Humor,” pg. B1, col. 1:
David Owens, 10, of Cub Scout Pack 33, Ewing Township asks:
 
“Why is six afraid of seven?”
“Because seven eight (ate) nine.”
   
1 January 1989, Philadelphia (PA) Inquirer, “The Best and Worst of ‘88 Films” by Carrie Rickey, pg. H1:
BEST JOKE
“Why is 6 afraid of 7? Because 7 8 9.”
- Tom Hanks in Punch Line.
 
Google Books
Take Me to Your Liter:
Science and Math Jokes

By Charles Keller
Illustrated by Gregory Filling
New York, NY: Scholastic
1991
Pg. ?:
Why was 6 afraid of 7?
Because 7 ate 9.
 
Google Books
Happy Birthday Lexie!
By Lisa Eisenberg
New York, NY: Viking
1991
Pg. 6:
“Speaking of riddles, I heard a great one today. Why is six afraid of seven?”
 
Google News Archive
25 August 1992, Spartanburg (SC) Herald-Journal, “The Stroller” by Lou Parris, pg. B1, col. 1:
From our InfoTouch joke line:
 
Why was six afraid of seven? Because seven ate nine.
 
Google Books
Kids’ Computer Creations:
Using Your Computer for Art & Craft Fun

By Carol Sabbeth
Charlotte, VT: Williamson Publishing Company
1995
Pg. 120:
Why was 6 afraid of 7?
Answer: Because 7, 8, 9!
 
OCLC WorldCat record
Why is 6 afraid of 7? : and other number jokes
Author: Chris Tait; Anthony Joseph Falcone
Publisher: Chicago, IL : KidsBooks, ©2000.
Edition/Format:   Print book : Juvenile audience : English
Database: WorldCat
Summary:
A collection of jokes and riddles all with a math theme.
 
YouTube
So…Why is Six Afraid of Seven?
Quality over Quantity
Uploaded on Aug 20, 2007
Mileah’s favorite joke.