Copyright © University of Cambridge. All rights reserved.
We had a number of correct solutions including
some from students from Our Lady's G.S. Newry, several from
students from Marist College in New Zealand (Kate and Lauren, Aimee
and Hannah, Jessica and Alesha, Helen and Maiya), Ben, Alex, Rob
and Harry from the Royal Latin School, Niall, Tyler, Daniele,
Michael and Thomas from St.Margarets C.E.Primary School, Ben, Beth,
Caitlin, Connor H, Connor L, Flora and Harry from Maynards Green
Primary School, Kai, Harry and William from Herbert Strutt School,
Bandhagi from The Garden International School and Charlotte, China,
Kyle, Viva, Dannielle, Jordan and Emily, all from Kavanagh
The Maths Challenge Group from Colyton Grammar
School sent a very clear explanation of how they arrived at the
As a start, we organised the cards into categories:
Facts about the obelisk
Facts about time measurement
Facts about workers
We also found that there were a number of cards that were
irrelevant to the solution.
Given the dimensions of the obelisk, we found that its volume is
100 x 50 x 10 = 50,000 cubic feet.
As each block is 1 cubic foot, this would require 50,000 blocks to
As the group size was 9, but one could not work, 8 people would be
working on the obelisk.
In addition, as the day was nine schlibs long, but the workers rest
for sixteen ponks (which equates to two schlibs), each worker would
be building for seven schlibs a day.
They would each be able to lay 150 blocks per schlib, and per day
this is 150 x 7 = 1050.
The whole group would therefore be able to lay 1050 x 8 = 8400
blocks a day.
Consequently, the obelisk would take a total of six days to
complete, as in six days they could lay 8400 x 6 = 50,400 blocks
(in five days this total would only be 42,000 blocks).
The Atlantian week has 5 days but only 4 of those would be spent
working, so the work would be completed on the 2nd day of the 2nd
week, which is Neptiminus.
Very similar thinking was used by Karim
from Wilson's School:
1. The dimensions of the zin indicate that it contains 50,000 cubic
feet of stone blocks.
2. The blocks are 1 cubic foot each, therefore, 50,000 blocks are
3. Each worker works 7 schlibs in a day (2 schlibs are devoted to
4. Each worker lays 150 blocks per schlib, therefore each worker
lays 1050 blocks per day.
5. There are 8 workers per day, therefore 8,400 blocks are laid per
6. The 50,000th block, therefore, is laid on the sixth working day.
7. Since work does not take place on Daydoldrum, the sixth working
day is Neptiminus.
is Mark's clearly laid out solution.
Edwin, Aufar, Hyeon and Dylan from B.S.M
Muscat in Oman also found out that they finished building the
Obelisk on Neptiminus. They added:
This puzzle was amazing!
Glad you enjoyed it. Well done to you