December 2013



Asteroid Science: Astronomers viewing our solar system's asteroid belt with NASA's Hubble Space Telescope have seen for the first time an asteroid with six comet-like tails of dust radiating from it like spokes on a wheel. Read more ....

Batteries through biology Lithium-air batteries have become a hot research area in recent years: They hold the promise of drastically increasing power per battery weight, which could lead, for example, to electric cars with a much greater driving range. MIT researchers have found that adding genetically modified viruses to the production of nanowires - wires that are about the width of a red blood cell - could help in making better batteries. Read more ....

Lithium ion battery Researchers have made the first battery electrode that heals itself, opening a new and potentially commercially viable path for making the next generation of lithium ion batteries for electric cars, cell phones and other devices. Read more .....

Plants and trees Rain as acidic as undiluted lemon juice may have played a part in killing off plants and organisms around the world during the most severe mass extinction in Earth's history. Read more ....

Water droplet Those who study hydrophobic materials - water- shedding surfaces such as those found in nature and created in the laboratory - are familiar with a theoretical limit on the time it takes for a water droplet to bounce away from such a surface. But MIT researchers have now found a way to burst through that perceived barrier, reducing the contact time by at least 40 per cent. Read more ....

Merging black holes Throughout our universe, tucked inside galaxies far, far away, giant black holes are pairing up and merging. As the massive bodies dance around each other in close embraces, they send out gravitational waves that ripple space and time themselves, even as the waves pass right through our planet Earth. Read more ....




Solution

Did you say the answer was 20 seconds - the LCM of 1, 2, 4 and 5? I think it is not 20 but 30 seconds. It is the one second for which the words glow, that is causing all the mischief.

Just for the ease of understanding, imagine that each word immediately upon lighting up lets off a small beep. The first word, therefore, gives a beep on lighting up. It remains glowing for one second and, then, goes off for one second. Then, it glows again after making a beep. So, the interval between the two beeps is two seconds.

Similarly, the second word gives a beep on lighting up; remains glowing for one second; and, then, goes off for two seconds. It lights up again, giving a beep. In this case, the interval between two beeps is three seconds.

Likewise, the interval between two beeps by the third word will be five seconds, and by the fourth word will be six seconds.

All the four words will light up simultaneously after beeping at the same time. That will happen after 30 seconds - the LCM of 2, 3, 5 and 6. So, I think the answer is 30 seconds. All the four words will glow together at intervals of 30 seconds.

You don't think I am right? Okay, I have tried to create a table. The time under the "Time" column is in seconds; I am not interested in the hour and minute part. Thus, initially, all the words are in OFF position. From 01 to 02 seconds, the first words glows, and the others are OFF; from 02 to 03 seconds, the first word goes OFF for a second and the others are also OFF. That is how it continues. This is what I get:

Time New Pankaj Super Shoppe
00-01 OFF OFF OFF OFF
01-02 ON OFF OFF OFF
02-03 OFF ON OFF OFF
03-04 ON OFF OFF OFF
04-05 OFF OFF ON OFF
05-06 ON ON OFF ON
06-07 OFF OFF OFF OFF
07-08 ON OFF OFF OFF
08-09 OFF ON OFF OFF
09-10 ON OFF ON OFF
10-11 OFF OFF OFF OFF
11-12 ON ON OFF ON
12-13 OFF OFF OFF OFF
13-14 ON OFF OFF OFF
14-15 OFF ON ON OFF
15-16 ON OFF OFF OFF
16-17 OFF OFF OFF OFF
17-18 ON ON OFF ON
18-19 OFF OFF OFF OFF
19-20 ON OFF ON OFF
20-21 OFF ON OFF OFF
21-22 ON OFF OFF OFF
22-23 OFF OFF OFF OFF
23-24 ON ON OFF ON
24-25 OFF OFF ON OFF
25-26 ON OFF OFF OFF
26-27 OFF ON OFF OFF
27-28 ON OFF OFF OFF
28-29 OFF OFF OFF OFF
29-30 ON ON ON ON


Some useful links for
your career:


  • Union Public Service Commission - www.upsc.gov.in
  • IIT-Kharagpur - www.iitkgp.ac.in
  • Indian Statistical Institute - www.isical.ac.in
  • Indian Institute of Technology Madras - www.iitm.ac.in
  • Indian Institute of Management, Ahmedabad - www.iimahd.ernet.in
  • Indian Institute of Mass Commission - www.iimc.nic.in
  • IIT Bombay - www.iitb.ac.in
  • Indian School of Mines, Dhanbad - www.ismdhanbad.ac.in
  • Birla Institute of Technology, Ranchi - www.bitmesra.ac.in
  • Central Institute of Fisheries Nautical and Engineering Training - www.cifnet.nic.in
  • Indian Institute of Information Technology, Allahabad (Deemed University) - www.iiita.ac.in
  • Central Marine Fisheries Research Institute, Kochi - www.cmfri.com
  • Tata Institute of Social Sciences, Mumbai - www.tiss.edu

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