NOTE: Newest BTs in red, Bonuses in blue, comments in green, updates in purple.
- (An old classic!) Your unorganized sock drawer contains 18 white socks and 18 blue socks. How many times do you need to reach inside the drawer and take out a sock at random to guarantee you have a sock of each color?
- A cowboy rode into town on Friday. He stayed in town for three days and rode back out on Friday. How is this possible?
- A palindrome is a number that reads the same forwards and backwards (like 202 or 454). How many palindromes are there between 100 & 1000?
- (A future hypothetical twist to a BT from last time) The 52nd and 54th Presidents of the US have the same mother and father, but are not brothers and are not the same man. How can this be?
- A woman was in her hotel room when there was a knock on the door. When she opened the door slightly, there was a man she’d never seen before. He said, “I’m sorry, I have made a mistake, I thought this was my room” and walked away. The woman went back into her room and phoned security. Why was the woman so suspicious?
- a) How many ways are there to re-arrange the letters in the word ‘STOP’ ? b) How many of those form a common-usage word?
- Augustus De Morgan was a mathematician who lived in the 19th century. He once wrote, I was x years old in the year x2. a) How old was he when he said that? B) What was his birth year?
- Several years ago, I drove a nail into a tree exactly five feet above the ground. The tree grows at the rate of one half-foot a year. Eleven years later, I returned to the tree. How far above the ground was the nail?
- A man wanted to encrypt his password but he needed to do it in a way so that he could remember it. He had to use seven characters consisting of letters and numbers only (no symbols like ! or <). In order to remember it, he wrote down “You force heaven to be empty.” What is his password?
- Guess the next three letters in the sequence: GTNTL.
- (Repeat) A digital clock forms palindromic times 114 times each day. What is A) the least, and B) the most amount of time between two palindromic clock numbers?
BONUS1: There are three light switches outside of a room: #1, #2, and #3- They are connected to three light bulbs inside the room. The door to the room is closed and you can’t see in. All three switches are currently off. You need to figure out which switch belongs to which bulb. You can use the switches however you want to, but can only enter the room once. How do you do it?
BONUS 2: The Jan/Feb BTs mention Year Product Days (For reminder, see Item 4 of this link.) Are there any YPDs in each century with seven (7) or more YPDs?
BONUS 3: A golf ball falls randomly onto a circular green 10 meters in radius, with the cup at the center. What is the probability that the ball is within 1 meter of the cup?
BT#1…19 reaches into the drawer.
BT#2…The horse’s name was Friday.
BT#3…90 whole numbers that are also palindromes between 100 and 1000.
BT#4…They are brother and sister (Don Jr and Ivanka?).
Turn on switch #1 and leave switch #2 in the off position.
Turn switch #3 on and count to 100 and then turn it off. Enter the room. The light that is lit is operated by switch #1. Of the two unlit bulbs, the one that is warm (assuming all are within reach…wasn’t excluded in the premise) is operated by switch #3 and the other by switch #2.
1. It is possible to pull 18 white socks in a row and then on the 19th try a blue sock will be pulled. The answer is 19 pulls.
2. He walked out of town and spent the other four days at a farm house. He returned to town, retrieve his horse, and rode out on the next Friday.
3. 90
4. They are sisters or brother-sister
5.
BT#6…There are 24 ways to rearrange the letters in STOP but only 6 will be common usage words.
BT#7…DeMorgan was 43 in 1849 when he said it, though it could have been any year after that and it still would not change the fact that he was born in 1806.
BT#8…10.5 feet above ground.
Admittedly, i often find myself skipping this section.
You indicated ‘not terribly hard’. Maybe i’ll get the hang of it, but i’m ready for the ‘reveal’ to these riddles!!
You’re certainly not the ONLY one who skips this section usually!! (Indeed, you’re probably in the majority :-)). But, there ARE folks who like them, so . . .
As you may have noted, Answers (and correct submitters) are always posted at the end of the (usually two-month) cycle, so that’ll be end of April or so this time. (If you NEED answers to the ones there now before that time, holler at me, and we’ll see what we can do. 🙂 )
Also, I’m aware that one person’s ‘not terribly hard’ is another person’s ‘difficult’ sometimes, but still, I suspect you could get some. Holler if questions.
Larry
I find myself wanting more on the ‘process’ of the answers, vs ‘the answers’ themselves.
I’m guessing that might be a bit much for this forum. (?)
Hi Christine – Hooray!! Wanting to know more about the ‘process’ than the ‘answers’ is GREAT!!! From a narrower educational point of view, it’s a step we WANT for students, but don’t succeed in getting often enough (Hmmm – could that be our/the system’s fault? Don’t get me started. :-))
It may or may not be ‘a bit much’ for this location (though I’d LOVE to see some discussions, hints, questions, going on!), but I’m sending you a separate e-mail and will be glad to explore it more if you’re interested!
Larry
Bonus#2…Any year which ends in 24 (such as 1924) would have 7 YPD’s…Jan 24, Feb 12, Mar 8, Apr 6, Jun 4, Aug 3, Dec 12.
BT#9…Password is U4cH2BE.
BT#10…The next 3 letters are ITS.
BT#9…Password is U4cH2BE.
BT#10…The next 3 letters in the sequence are I, T, and S.
1. 3
2. Horse’s name is Friday
3. 90
4. They are sisters or brother and sister
5. He knocked inside of using his key.
6.A-24 B-4
8.5 ft. I don’t think the nail would grow up.
10. TJT
1. 19 times
2. His horse’s name is Friday
3. 90 palindromes
4. They are brother and sister
5. Because a guest in a hotel would not knock on the door of their own room
6. a) 4! = 24 ways
b) 6 are common words (STOP, POTS, TOPS, SPOT, OPTS, POST)
7. a) 43 years old
b) born in 1806
8. 21.5 ft. above ground
9. U472BMT
10. ???
11. A) 10 min. B) 1 hr. 10 min.
12. boy #4 will make himself fall to the ground without affecting any of the others
Bonus 3: 1/100 or 0.01 or 1%