ERJ Brainteaser: April

Question 4: What’s another…?

I69I, I88I, I96I, _?

Answer: These are numbers/years that are the same when inverted - also known as strobogrammatic numbers. So, the next year is 6009. Well done to: Hans-Bernd Lüchtefeld, marketing manager, Indorama Mobility Group, Germany; John Bowen, rubber industry consultant, Bromsgrove, Worcs, UK; Andrew Knox, Rubbond International, Ohé en Laak, The Netherlands; David Mann, key account manager, SPC Rubber Compounding, UK; Michele Girardi, Scame Mastaf Spa, Suisio, Italy;  Yoganand Nannapaneni, Mascot Systems Pvt. Ltd, Vashi, Navi Mumbai, India; Stephan Paischer, head of product management and market intelligence, Semperit AG Holding, Vienna, Austria; and every one else who had a go.

Solutions

Best reply:

Andrew Knox

Assuming the title of this question refers to Johnny Logan's song "What's another year", then this sequence is probably a sequence of years in which the numbers can be rotated through 180 degrees and still read the same, so-called strobogrammatic numbers. So the next in the sequence is 6009, then 6119, etc…

Next teaser on Tuesday, due to UK bank holiday.

Question 3: What comes next?

2, 3, 3, 5, 10, 13, 39, 43, 172...

Answer: As neatly explained by Hans-Bernd Lüchtefeld (and others) the pattern is + 1, x 1, + 2, x 2, + 3, x 3, + 4, x 4, + 5…. So, the next two numbers are 177 and 885. Very well done to: John Bowen, rubber industry consultant, Bromsgrove, Worcs, UK; Michele Girardi, Scame Mastaf Spa, Suisio, Italy; Hans-Bernd Lüchtefeld, marketing manager, Indorama Mobility Group, Germany; Andrew Knox, Rubbond International, Ohé en Laak, The Netherlands; Yoganand Nannapaneni, Mascot Systems Pvt. Ltd, Vashi, Navi Mumbai, India; Mehmet Koral, Erhardt-Leimer representative for Turkey, managing director, C&C Endüstriyel Danismanlik, Egitim ve Mümessillik Ltd, Göztepe, Istanbul; and everyone else who had a go.

Solutions:

As well as the neat replies similar to above, our judges appreciated Michele Girardi’s ‘formulaic’ approach to the problem:

A(n)=(n-1)*B(n-1)

B(n)=A(n)+n

N A(n) B(n)

1 2 3

2 3 5

3 10 13

4 39 43

5 172 177

Question 2: Fill in the gap
 
11111100100, 11111100101, ____ , 11111100111, 11111101000 

Answer: For many a blur of random I/O digits, for our seasoned Brainiacs clearly 2020, 2021, ___, 2023, 2024, written in binary code – making the missing number 11111100110 (ie 2022). Very well done to: Dr Katharina Gottfried, TSAD manager, Arlanxeo Deutschland GmbH, TSAD EMEA II, Koeln, Germany; Joe Suter, financial manager, Endurica LLC, USA: John Bowen, rubber industry consultant, Bromsgrove, Worcs, UK; Stephan Paischer, head of product management and market intelligence, Semperit AG Holding, Vienna, Austria; Andrew Knox, Rubbond International, Ohé en Laak, The Netherlands; Jose Padron, material development specialist, Waterville TG Inc. Waterville, Québec, Canada; Michele Girardi, Scame Mastaf Spa, Suisio, Italy; David Mann, key account manager, SPC Rubber Compounding, UK; and everyone else who had a go.

Some really neat replies, with the solution perhaps best illustrated by Jose Padron’s table:

Question 1: Country file

What have these countries (listed in alphabetical order) in common?

... Greece, Switzerland, UK, Uruguay...

Answer: Our first teaser of April seems to have been a bit obscure for many. Extra well done, so, to Andrew Knox, Rubbond International, Ohé en Laak, The Netherlands; and Michele Girardi, Scame  Mastaf Spa, Suisio, Italy; who found that these countries were the inaugural hosts of major international sports/entertainment events: respectively the modern Olympics (Athens, 1896); the Eurovision song context (Lugano, 1956); ‘grand slam’ tennis tournament (Wimbledon, 1877); men’s football world cup (Montevideo, 1930).