London stock exchange has recently gone geek, putting an end to the face-to-face (and boisterous) transactions. The too-quiet LSE headquarters doesn't have the usual bell to signal the beginning or end of a trading day. Instead, the nerdy officials have installed a giant abacus-like structure as a centre-piece. The huge installation, called Source, consists of 729 spheres suspended from 81 pairs of cables. Each strand stretches a span of a 105-foot atrium, and every sphere runs on an internal motor. Connection to a server helps spherical orbs form abstract patterns and words, everything from a double-helical structure of a DNA, pound-dollar-euro signs or even the matter-of-fact M--N-E-Y. The artist programmer, however, recently told Wired magazine that he'd initially planned to design the popular game Tetris, showing changing patterns of square blocks.

PUZZLE 1: A man falls overboard and gets washed ashore on an island with nothing but sand. The island is 50 miles from the nearest land. He can't swim, the water's 100 feet deep, and the island has nothing to make a floatation device with. With no help from people, animals or fish he finds a way off the island. How come'

PUZZLE 2: You are attending a meeting where only accountants and lawyers are present. From your previous dealings with people belonging to these two professions, you know that accountants always tell the truth about everything and lawyers always lie about something. Two gentlemen, Sam and Adam, approach you. Sam introduces himself and says, 'I am a lawyer, but Adam is an accountant.' Based on what you know already, what are the professions of Sam and Adam'

PUZZLE 3: A man named Tom walks into a restaurant for lunch. He asks the waitress if she is good at solving puzzles. She replies, 'I am the best.' So Tom says he'll have 'sausage and noodles drenched with ice cream, hashed,' and adds, 'if you bring me what I really want I'll leave you a $100 tip.' A few minutes later, she brought him exactly what he wanted, and he left her the large tip. What did Tom really eat for lunch'

Solutions on February 21

CORRECT ENTRIES

January 31

Amitabh Roy Sharma, Bokaro Steel City;Abhinandan Khan, Dum Dum; A. K. Majumdar,Cal-106;Debabrata Sengupta, Dum Dum; Deepankar Garg;Debasis Ganguly,Alumnus Software Ltd; Arunabha Sengupta,TCS-Cal;Abhigyan Mundhra,Apeejay School;Pramit Mukherjee, Serampore;Deepak Kumar Agarwal, College of Ceramic Technology;Arko Barman, Cal-1;Gaurav Konar,Cal-1; S.P. S. Jain, New Delhi; Debasish Paul, Cal-13; Radhamohan Kejriwal, Ranigunj; S. Krishnaiyer, Cal-8.

Please send your entries to knowhow@abpmail.com within 10 days. Mention the date of the puzzle in the message box.

PUZZLE CRACKED

Solution 1: There are 4'6=24 different 5-digit numbers that are divisible by 12. Hint: 12=3'4; in other words, if a number is divisible by 12 it will be divisible by 3 and 4 also. For a number to be divisible by 3, the sum of its digits must be divisible by 3: 1+2+3+4+5=15. As 15 is divisible by 3, all the five-digit numbers made up of the digits 1, 2, 3, 4 and 5 will be divisible by 3.

Solution 2: x=a/6

Solution 3: The probability of a number with increasing digits containing exactly five digits is 126/511=18/73. Hint: Each non-empty subset taken from {1,2,3,4,5,6,7,8,9} represents each of the possible numbers with strictly increasing digits, and in turn each of these subsets can be represented by a 9-digit binary string.

The puzzles appeared on January 31