ERJ Brainteaser - June

Question 2: Countdown conundrum

207.65, 100.91, 43.03, 19.30, _?_.

With apologies, due to a technical blip, the promised clues were not issued for this teaser. We have, therefore, decided to continue the question into next week...

...with the clues: Cu/Sn, Ag, Au.

Email your answer.

Please also note: Due to staff holidays the correct replies will be issued on Monday 22 June, along with the next Brainteaser. 

3, 11, 19, 37, 55, ?.

Clues: Metal, Group...

Answer: 87 for Francium. Extra well done to: Andrew Knox, Rubbond International, Ohé en Laak, The Netherlands; Amparo Botella, responsable de Compras y Calidad, Ismael Quesada SA, Elche, Alicante, Spain; John Bowen, BSc [Hons], CEng, MIMMM, consultant, Bromsgrove, UK; Kamila Staszewska, R&D / quality lead, Abcon Industrial Products Ltd, Cootehill, Co. Cavan, Ireland; Dr Kate Burns, senior technologist and regulatory officer, Prisma Colour Ltd, Birch Vale, High Peak, Derbyshire, UK; Bharat B Sharma, technical director TWC Group (Techno Waxchem & Rajsha Chemicals), Kolkata, India; Hans-Bernd Luechtefeld, consultant, Germany; and everyone else who had a go. 

SOLUTIONS

Andrew Knox

STAR ANSWER: Replied before seeing any clues… or even the French connection!

Answers:

1. If this were a mathematical sequence then one answer would be 83.

Taking the differences between the numbers gives 8, 8, 18, 18, and repeating this step gives 0, 10, 0, giving a repeating pattern of 0 and 10 to predict the next number as being  10+18+55=83. A bit weak but it works in the sense that a pattern has been found that can be used to predict the next numbers in the sequence.

1. Probably a better answer is that this sequence is based on the atomic numbers of the alkali metals (Group 1 elements) in the periodic table:

3: Lithium (Li)

11: Sodium (Na)

19: Potassium (K)

37: Rubidium (Rb)

55: Cesium (Cs)

87: Francium (Fr)

Still no idea what led to the question being asked in French...

{I was] thinking it must have something to do with Paris St. Germain beating Arsenal....

Amparo Botella

I think we refer to the atomic numbers of Alkali metals in the chemical elements periodic table:

3-Tithium

11-Sodium

19-Potassium

37-Rubidium

55-Cesium

So next on will be 87-Francium

The reply is 87.

John Bowen

Next number is 87.

These are the atomic numbers of Group 1 metals - Lithium, Sodium, Potassium, Rubidium, Caesium, next with Atomic Number 87 is Francium.

[A bit slow to spot the Rule of Octaves...]

Kamila Staszewska

The answer lies - quite literally-  on the periodic table of elements (first column=alkali metals).

3-Lithium , 11-Sodium, 19 -Potassium, 37-Rubidium, 55-Cesium and the answer: 87-Francium (hence the question).

Voilà!

Dr Kate Burns

The next number in the sequence is 87, s'il vous plaît. The sequence is the atomic numbers of the Alkali metals, ending in Francium, 87. 

Bharat B Sharma

Based on clue, it’s the list of metals and that too of group 1 of periodic table (Alkali Metals).

The answer will be 87

Detail--

The rule of given sequence

The numbers are the atomic numbers of the chemical elements appearing in the first column of the periodic table (Group 1) also known as known as alkali metals.

• 3 : Lithium
• 11 : Sodium
• 19 : Potassium
• 37 : Rubidium
• 55 : Cesium
• 87 : Taking the clue further, we get the Francium Fr

Hans-Bernd Luechtefeld

87 for Francium

The numbers (3, 11, 19, 37, 55, ?=87) represent the chemical elements in Group 1 of the periodic table. They are also known as the alkali metals:

3 = Lithium (Li)

11 = Sodium (Na)

19 = Potassium (K)

37 = Rubidium (Rb)

55 = Cesium (Cs)

87 = Francium (Fr)

New teaser on Monday.