# How many segments are lit on a Seven Segment Digital Clock?

Marilyn is Wrong **Copyright © 2006 Herb Weiner. All rights reserved.**
**Ask Marilyn ®** by Marilyn vos Savant is a column in *Parade Magazine*,
published by PARADE, 711 Third Avenue, New York, NY 10017, USA.
According to Parade, Marilyn vos Savant is listed in the
"Guinness Book of World Records Hall of Fame" for "Highest IQ."

In her *Parade Magazine* column of July 2, 2006, Marilyn states that the last number in the sequence 19, 15, 18, 18, 17, 18, 19, 16, 20, 19, which repeats after 720 numbers, is 14, which represents 11:59 on a seven segment digital clock.

## Sorry, Marilyn

Ronald Niles ron@ronniles.com observed an inconsistency in Marilyn's answer:
Although Marilyn correctly recognizes the puzzle, the
last number in the sequence, representing 11:59 is 15,
not 14.

This could be simple mistake in math, but that is
unlikely. More likely it is due to the different ways
in which digital clocks represent the digit 9. Some
use six segments to do it, and others omit the segment
on the bottom, using only five. The former case would
result in the last number in the sequence being 15,
the latter case would result in 14. Since the reader
who posed the question was clearly using a clock which
uses six segments to represent the digit 9, the only
correct interpretation of the last number in the
sequence is 15.

http://www.wiskit.com/marilyn/sevensegment.html last updated August 9, 2006 by herbw@wiskit.com