
Welcome to the International Skeptics Forum, where we discuss skepticism, critical thinking, the paranormal and science in a friendly but lively way. You are currently viewing the forum as a guest, which means you are missing out on discussing matters that are of interest to you. Please consider registering so you can gain full use of the forum features and interact with other Members. Registration is simple, fast and free! Click here to register today. 
19th January 2017, 03:04 PM  #1 
Master Poster
Join Date: Jan 2013
Posts: 2,366

Quiz
Who want to be a millionaire had their Whiz Kids series and the asked a math question. So the kid had to figure this out entirely using his brain.
They gave the number 123456787700000 (actually they listed the last digits but I forgot what they were) and asked what was the square root. There were multiple choices a. 11111111, b. 1111111, c. 111111. How would you work this out in your head. The Whiz kid did. I have a procedure in mind but not the way he did it. 
__________________
Trouble walks in on small delicate feet and grows 

19th January 2017, 03:24 PM  #2 
Penultimate Amazing
Join Date: Feb 2006
Posts: 29,167


19th January 2017, 04:31 PM  #3 
Scholar
Join Date: Dec 2004
Posts: 123

Based on the example answers, let's assume the number was probably 123456787654321.
It's a (somewhat?) wellknown math trick: take a number made up from a series of ones and square it. It will produce a palindrome 2n1 digits long where n is the number of digits in the original number. So 123456787654321 is 15 digits long. (15+1)/2 = 8. So the square root would be 111111111 (eight ones). 
__________________
"The greatest obstacle to discovery is not ignorance  it is the illusion of knowledge."  Daniel J. Boorstin 

19th January 2017, 04:39 PM  #4 
Graduate Poster
Join Date: Jul 2010
Location: Silicon Valley
Posts: 1,365

Given those choices, you don't have to worry about anything except the length. The given number starts with a 1, so it's pretty close to 10^14. The square root of that will be 10^7 (an eight digit number starting with 1). Pick the eight digit number.

Bookmarks 
Thread Tools  

