Mathematician daughters age problem?

Problem:
Two old friends(Mathematicians) meet each other after 20 years.Lets call them A,B.
A says to B: “how have you been?”
B says: “Great! I got married and I have three daughters now”
A says: “Really? how old are they?”
B says: “Well, the product of their ages is 72, and the sum of their ages is the same as the number on that building over there..”
A says: “I still don’t know”
B says: “The oldest one just started to play the piano”
A says: “my oldest is the same age!”

Solution:

This is simple mathematical problem which can be solved by applying simple logical reasoning in the case of ambiguity.
After first clue A couldn't answer the question just because there might be two sets of three numbers which produce product of 72 and the sum of numbers in both the sets is equal.
After simple calculation we can reduce on two following two sets where sum of numbers is equal.
(8,3,3) & (6,6,2)
In second case two elder kids are of same age, so you cannot pick an “oldest”. Answer is (8,3,3) hence.

Why are manhole covers round rather than square?

This Question was most interviewer's favourite question for years. I hardly find anyone asking it these days. Answer to this question involves some simple maths with commonsense.
All of us know that circle has same diameter in all directions so no matter how you hold it cover cannot be pushed into a circular manhole. Whereas, if it is square, cover can be pushed into manhole via diameter by holding it on edge. Another aspect is, if cover is circular it is easier to roll it so for shorter distances transportation is easy.

Free domain+disk space offer from one.com

Today i have seen a good webhosting offer from one.com for indian customers.
They are giving 3000M diskspace + domain name for free for first 12 months.
We need to pay only 13.8 USD. I think there is some moneyback offer for 15 days if you are not satisfied with their service. Here is the link http://www.one.com/en_US/.

I have talked to their customer care executive about this offer.
Here is the excerpt of the same. Arjun is their customer care executive.

you: i want to know about free domain + hosting offer
Arjun: hI
Arjun: As a promotion in India, we are offering domain name and 3000MB web space absolutely free for the first year. So all you need to pay is a minimal setup fee of 13.8 USD
you: how long this offer will be active
you: when is the last day to apply
Arjun: there is no end date announced yet
you: ok
Arjun: Is there anything else I could assist you with?
you: can i put the adsense
you: on the site hosted with this offer
Arjun: yes
you: any site templates available from one.com
you: is it possible to put forums on this site
Arjun: yes
Arjun: we offer templates and yes you can install a forum
you: thanks
you: is there any offline payment option available in india
Arjun: unfortunately, no

Simulate seven sided die using 5 sided die?

This Question is asked in different formats like simulate rand7() using rand5() function.

There is no right answer to this question if interviewer specifies that 7 sided die should have equal probability to al the numbers on it(i.e. 1-7). This is because 5 and 7 are coprime and there is no direct mapping available between coprimes.
There are several solutions which creates a biased 7 sided die.
Sol1:
Throw 5 sided die 7 times. sum will be between 7 and 35, with equal probable numbers. Then take the module 7 of the sum and add 1 to it.
This solution will produce biased die because probability of 1 is higher here.

Sol2:
rand7() = ((ran5() + rand5() + rand5() + rand5() + rand5() - 5) % 7) + 1

Alternative earnings through internet.

Modern day students need not depend on their parents or elders for the pocket money. With the widespread use of internet there are lot of opportunities available for making money online. There are couple of online survey sites based in india which are providing reward points for filling up simple surveys ( http://xcel-onlinesurveys.com?sid=1&rid=AF24257&aid=0).
Lot of online work portals like rentacoder.com etc.. which provides works ranging from homework help to large industrial automation projects in the field of IT.

microsoft livesearch win rewards

Live.com microsoft's search initiative introduced a new feature which enables users to play the video search results with mouseover. This is one of the scoring points for Live.com apart from host of incentives you get by searching with Windows Live search engine.

Microsoft has comeup with free talktime offer to popularize there search. Click on the below link to find out more.
http://winwithsearch.com

Their searchperks program where you can win gifts based on the reward points in still on. Last date to register is 31st December,2008. Below link have the details.

http://www.getsearchperks.com/
I don't know whether it helps in popularizing their search , but certainly helps users in winning prizes.

There are 25 horses and only 5 tracks. No of matches to find top 3 horses.

Problem:
There are 25 horses and only 5 tracks. So only 5 horses can run the race at a time. How many minimum no of races should be conducted to find the 3 best horses?
Sol: The answer is 7.
Round 1: Take 5 horses at a time. 5 winners of each race will go to round2.
Round 2: Winner of this will be top most horse.(call it W1)
Round 3: Final race comprises of following 5 horses.
h1: 2nd horse of round2
h2:3rd horse of round2
h3:2nd horse of W1's group during round 1
h4:3rd horse of W1's group during round1
h5:2nd horse of h1's group during round1

Hat color problem--most asked question in interviews..

http://en.wikipedia.org/wiki/Prisoners_and_hats_puzzle