ERJ Brainteaser: July 2019
19 Sep 2019
Having responded correctly to all four questions of the month, Ramasubramanian P of Larsen & Toubro Ltd in India, deservedly wins the Brainiac of the Month title.
Find the missing number in the table above.
Answer: 55 – a relatively easy one which saw many new entrants.
Well done to Lars Linnemann, R&D manager, Genan A/S, Viborg, Denmark; Bharat B Sharma, Sr VP Product Development & Technical Service (Elastomers), Reliance Industries Ltd, Vadodara, Gujarat, India; Sebastian Barbe, group operations manager Hans W. Barbe Chemische Erzeugnisse GmbH, Germany; Stephan Paischer, head of product management special products, Semperit AG Holding, Vienna, Austria; Sajiva Manju; David Cao; John Droogan, advanced polymers and composites, MegaChem (UK) Ltd, Caldicot, Monmouthshire, UK; Michele Girardi, Scame Mastaf Spa, Suisio, Italy; John Bowen, consultant, Bromsgrove, UK; France Veillette, chef environnement, Usine de Joliette, Bridgestone Canada Inc., Canada; Andrew Knox, Rubbond International, Ohé en Laak, The Netherlands; Ramasubramanian P, manager, marketing – mixer and LTKMPL products, rubber processing machinery, Larsen & Toubro Ltd, Vedal Village, Kanchipuram, Tamil Nadu, India; Paul Knutson, textile engineer, Timken Belts, Springfield, Missouri, USA; Thierry Montcalm, R&D and innovation manager, Soucy Techno, Canada; Jose Padron, material development specialist, Waterville TG Inc., Waterville, Québec, Canada; Ricardo Azcarate; Serafina Vulcano; Fariha Rashid, marketing analyst, Kraton Polymers LLC, Houston, Texas, US. Berny Bolanos, PE Curing & Tire Room, Bridgestone Costa Rica
In a tire test, a race car is driven along a straight horizontal track with constant acceleration. There are three check points A, B and C, in that order, on the road, where AB = 22 m and BC = 104 m. The car takes 2 seconds to travel from A to B and 4 seconds to travel from B to C. What is the acceleration of the car, and the speed of the car at the instant it passes A?
Answer: Acceleration of the car = 5 m/s² and speed at point A = 6 m/s (see solution from below). Well done to: France Veillette, chef environnement, Usine de Joliette, Bridgestone Canada Inc., Canada; Paul Knutson, textile engineer, Timken Belts, Springfield, Missouri, USA; John Bowen, consultant, Bromsgrove, UK: Ramasubramanian P, manager, marketing – mixer and LTKMPL products, rubber processing machinery, Larsen & Toubro Ltd, Vedal Village, Kanchipuram, Tamil Nadu, India.
Bonus question: What is the minimum number of serves you would need to take, to be a victor in a three-set match of doubles tennis? The answer was, quite simply, 12 serves.
Fast car? solution from Ramasubramanian P:
Speeds at A,B,C are Ua, Ub, Uc
Acceleration is constant a.
Constant Accleration Formulae:
V = U + aT
D = UT + (1/2)aT^2
Using the above formulae,
Ub = Ua + 2a —- 1
Uc = Ub + 4a —- 2
Uc = Ua + 6a —- 3
22 = 2Ua + 2a —- 4
104 = 4Ub + 8a —- 5
126 = 6Ua + 18a —- 6
(6) – 9*(4): Ua = 6 —- 7
(6) – 3*(4): a = 5 —- 8
(7)&(8) on (1): Ub = 16 —- 9
(7)&(8) on (3): Uc = 36 —- 10
Acceleration of the car : 5 m^2/s: speed at instant A : 6 m/s
This was an adaptation of a problem by a well-known puzzler, Henry Ernest Dudeney (1857 – 1930) – as supplied in The Engineer magazine many years ago.
Last week, the squire and his wife held a party for the villagers. The guests comprised 3 widowers, 3 widows,9 bachelors and boys, 7 eligible maidens and girls, and 7 married couples.
The hosts and all guests kissed everybody else present once, with the following exceptions:
No male kissed another male;
No married man kissed a married woman except his own wife;
The widows did not kiss each other;
The widowers kissed only the widows;
All the bachelors and boys kissed all the maidens and girls twice;
Each kiss between two people counts as one kiss.
How many kisses were there?
Answer: The official answer, from all those years ago, was 472 kisses (see Henry Ernest Dudeney’s solution below). Well done to the following readers who got this correct and to the many others who had a really good go:
Michele Girardi, Scame Mastaf Spa, Suisio, Italy; Paul Knutson, textile engineer, Timken Belts, Springfield, Missouri, USA; Stephan Paischer, head of product management special products, Semperit AG Holding, Vienna, Austria; Ramasubramanian P, manager, marketing – mixer and LTKMPL products, rubber processing machinery, Larsen & Toubro Ltd, Vedal Village, Kanchipuram, Tamil Nadu, India.
The table below summarises the position: (males in upper case, females in lower case)
0=no kiss, K=1 kiss, T=2 kisses.
Or as Michele Girardi explained: This is done dividing the people in homogeneous groups and building a table of number of kisses considering the exceptions . The total is given by the sum of the diagonal and one of the quadrants.
Fill in the gaps in the following sequence:
Walker, ___, Herbert, Wilson, Earl, ____.
Answer: A chance to recharge your calculators this week, as we delved deep into the world of politics. The readers below (not the US presidents) correctly identified the sequence as:
George Walker Bush
William Jefferson Clinton
George Herbert W. Bush
Ronald Wilson Reagan
James Earl Carter
Gerald Rudolph Ford
Well done to: Stephan Paischer, head of product management special products, Semperit AG Holding, Vienna, Austria; Hans-Bernd Lüchtefeld, market research & communication manager, PHP Fibers GmbH, Obernburg, Germany; John Bowen, consultant, Bromsgrove, UK; John Droogan, advanced polymers and composites, MegaChem (UK) Ltd, Caldicot, Monmouthshire, UK; Andrew Knox, Rubbond International, Ohé en Laak, The Netherlands; Yuichi (Joe) Sano, Sumitomo Electric Industries Ltd, Itami, Japan. Jose Padron, material development specialist, Waterville TG Inc., Waterville, Québec, Canada; Ramasubramanian P, manager, marketing – mixer and LTKMPL products, rubber processing machinery, Larsen & Toubro Ltd, Vedal Village, Kanchipuram, Tamil Nadu, India.
