You’re meeting on old friend at his house after many years and can only remember that he had two kids. You have no clue if they were sons or daughters of one of each. While there, you’re introduced to one child who’s a boy. The other one you’re told is sleeping and have not yet met. Now (1) Given the above situation what is the probability that the sleeping child is also a boy? And (2) Your friend further informs you that the boy you have met is the elder of the two children. What is the probability now that the sleeping child is also a boy? Are the two probabilities different?
THROUGHPUT
(The BCE problem was: “A billionaire doesn’t have room in his garage for eight of his limos. So he increases the size of his garage by 50% which gives him room for eight more limos than he owns altogether. How many limos does he own?”)
The billionaire owns 40 limos. Initially his garage had space only for 32 limos and that space was not sufficient for the remaining 8 limos. As he increases the size of the garage by 50%, his garage becomes large enough for 48 limos. After parking all his 40 limos, there is still space for 8 more limos. -- Dr P Gnanaseharan, gnanam.chithrabanu@gmail.com
The 50% extra garage space holds the eight limos that could not be parked in the previous (tiny!) garage AND eight additional (swanky) ones, ie, 16 cars. Therefore, the original 100% space should have held twice this number of cars (32). Since he had eight more limos that had to face the elements without space to park, he had 40 limos in all. Maybe this one became a billionaire by renting his limos! -- Dr Ramakrishna Easwaran, drrke12@gmail.com
(Among the five who also got it correct are: U N Murthy, u_n_murthy@rediffmail.com; Dhruv Narayan, dhruv510@gmail.com; Vijayalakshmi Sudheer, vijisudheer62@gmail.com; Abhay Prakash, abhayprakash@hotmail.com; Shekar G P, shekargp@yahoo.com)
(The second problem was: “Can you replace the “?” with the correct three letters? voN luJ ? raM beF.”)
Ah! You have a devious mind -- inserting a puzzle within puzzle. I tried to write in all caps and small letters to see if there was a pattern. Immediately it became clear that it contains the first three characters of the month names written in reverse order with the first letter of the month in capital. From right to left, we get: Feb Mar ? Jul Nov. The second puzzle starts now. The only way I tried is to substitute the month with numbers resulting in 2, 3, ?, 7, 11. Series of prime numbers. The missing word corresponds to month #5 and should be yaM. -- Saishankar Swaminathan, saishankar482@gmail.com
(The third one was: “Six-year-old Raja made an indelible ink mark on a tree to indicate his height. Five years later at age eleven, he returned to see how much higher the mark was. If the tree grew by 7.5 cms every quarter, how much higher would it be?”)
The mark remains at the same place. Trees grow upwards from within, and the outer girth only thickens. We tied a clothesline 30 years ago; we still reach it at the same height! -- Narayanan P S, narayananpsn@gmail.com
Is this a trick question? If yes then I’d say adult trees do not grow vertically but only in girth. So Raja will find the mark at the same height. If he hasn’t grown any taller he will be at least a little wiser! -- Ajit Athle. ajitathle@gmail.com
The answer is neither 7.5*20 cms nor “Data is insufficient”. The mark may be indelible, but Raja won’t find it. It has gone under five annual rings of the stem surrounding it as the diameter of the stem has grown ring by ring every year during those five years. He would be perplexed but the curiosity would provide him an opportunity to learn how trees grow. -- Abhay Prakash, abhayprakash@hotmail.com
BUT GOOGLE THIS NOW
1. Manidoowaaling (original American-Indian name) island is the largest freshwater lake island in the world. It also holds another world record. What?
2. (We’ll start with a hint: this shoulnot take you more than 30 seconds but yes you’re obviously going to cheat before the “aha!” moment bites you on the head.) If it’s 6.45 pm right now, what’s the time going to be 23,999,997 hours later? (At least let us know how long it took for the aha guy to nibble your noggin.)
Sharma is a scriptwriter and former editor of Science Today magazine.(mukul.mindsport@gmail.com)