Geekery

Riddles: Your Number’s Up

Posted on 04. Nov, 2009 by Jake.

Things are getting trickier as the year comes to it’s inevitable and less than graceful close. Ain’t it feel good that in this crazy world some things – maybe not the weather in Jo’burg, but some things – always make sense. That is, if you can figure ‘em out

Riddle 1 for the week

What do the following numbers have in common? (tricky one, this…)
3    7    10    11    12

Riddle 2 for the week

What is the next number in this series?
5   25   61   113   181   ..

Answers to be put up on the 16th of November.

Answers to last week’s riddles:

Problem 1:
Take the letters ERGRO. Put three letters in front of it, and the same three letters behind to form a common English word.
UND(ERGRO)UND

Problem 2:
Which of the following words is the
odd-one-out?
IBIS IBEX ORYX SIKA ZEBU
Ibis is a bird the rest are mammals

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Riddles: The Really, Really, Really Big Number

Posted on 16. Sep, 2009 by Jake.

The Really, Really, Really Big Number

When you divide 12 by 5, the remainder is 2; it’s what’s left over after you have removed all the 5s from the 12.  When you raise 4 to the fifth power (that is, 45), you multiply four by itself five times: 4×4×4×4×4, which equals 1,024.

What is the remainder when you divide 100100 by 11?

The Unkindest Cut of All, Part 1 of 2

The area of a square is equal to the square of the length of one side. So, for example, a square with side length 3 has area (32), or 9. What is the area of a square whose diagonal is length 5?

Answers will be published on Tuesday the 29th of September

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Riddles: Teasing your brain in hotel’s. Sounds fun.

Posted on 01. Sep, 2009 by Jake.

Weekly brain teasers coming atcha. Hotels are always fun, so that’s our topic for the week.

Hotel Bill

Three people check into a hotel. They pay $30 to the manager and go to their room. The manager finds out that the room rate is $25 and gives the bellboy $5 to return to the guests. On the way to the room the bellboy reasons that $5 would be difficult to split among three people so he pockets $2 and gives $1 to each person. Now each person paid $10 and got back $1. So they paid $9 each, totaling $27. The bellboy has another $2, adding up to $29.
Where is the remaining dollar?

Small Hotel

13 people came into a hotel with 12 rooms and each guest wanted his own room. The bellboy solved this problem.
He asked the thirteenth guest to wait a little with the first guest in room number 1. So in the first room there were two people. The bellboy took the third guest to room number 2, the fourth to number 3, …, and the twelfth guest to room number 11. Then he returned to room number 1 and took the thirteenth guest to room number 12, still vacant.
How can everybody have his own room?

Answers to be posted on September 7th

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Oldest Piano Player on a Railroad Bridge Riddle

Posted on 21. Aug, 2009 by Jake.

Think you’re fast? Time yourself solving these riddles, submit your time in the comments section (…those who tell the truth get a noddy badge!)

The Oldest Plays the Piano

Two MIT math grads bump into each other while shopping at Fry’s. They haven’t seen each other in over 20 years.

First grad to the second: “How have you been?”
Second: “Great! I got married and I have three daughters now.”
First: “Really? How old are they?”
Second: “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…”
First: “Right, ok… Oh wait… Hmm, I still don’t know.”
Second: “Oh sorry, the oldest one just started to play the piano.”
First: “Wonderful! My oldest is the same age!”

How old was the first grad’s daughter?

Answer:

The possible ages ( factors of 72 ) and their sums are shown below:
Ages:            Sum of ages:
1 1 72            74
1 2 36            39
1 3 24            28
1 4 18            23
1 6 12            19
1 8 9             18
2 2 18            22
2 3 12            17
2 4 9             15
2 6 6             14
3 3 8             14
3 4 6             13

We can deduce from the man’s confusion over the building number that this wasn’t enough information to solve the problem. The chart shows the sum 14 twice for two different age possibilities, which would explain how knowing the building number alone would not have given him the answer. The clue that the “oldest one” started to play the piano rules out “2 6 6” as an answer, because there is no “oldest”. Since the first grad was certain with the piano clue, the first grad’s oldest daughter is 8. I’ll leave it up to the reader to figure out why this doesn’t necessarily mean the second grad’s oldest daughter was also 8.

Railroad Bridge

A man needs to go through a train tunnel.  he starts through the tunnel and when he gets 1/4 the way through the tunnel, he hears the train whistle behind him.  You don’t know how far away the train is, or how fast it is going, (or how fast he is going).  All you know is that:

1. if the man turns around and runs back the way he came, he will just barely make it out of the tunnel alive before the train hits him,
2. if the man keeps running through the tunnel, he will also just barely make it out of the tunnel alive before the train hits him.

Assume the man runs the same speed whether he goes back to the start or continues on through the tunnel.  Also assume that he accelerates to his top speed instantaneously.  assume the train misses him by an infintisimal amount and all those other reasonable assumptions that go along with puzzles like this so that some wanker doesn’t say the problem isn’t well defined.

How fast is the train going compared to the man?

Answer:

We know that the train and man will reach the start of the tunnel at the same time if the man turns around, in that time the man travels 1/4th the length of the tunnel. 

If the man travels on towards the end of the tunnel he will be able to travel an additional 1/4th of the length of the tunnel before the train reaches the start of the tunnel, putting the man at the half way point.

For both the man and the train to reach the end of the tunnel at the same time, the man has to travel 1/2 the length of the tunnel while the train has to travel the full length of the tunnel.

Therefore the train must be travelling twice as fast as the man (and as an aside must have been half the length of the tunnel away from the start of the tunnel when it blew its whistle).

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Riddles: palindromes & Camels

Posted on 03. Jul, 2009 by Jake.

Palindromes

Each pair of hints below relates to two words. One of the words is the other one spelled backward.
Example: married, moisture
Answer: wed, dew

1. light source, rodents
2. dwell, wicked
3. retain, sneaking look
4. weapons, tight fit
5. portion, catching device
6. prize, furniture compartment
7. drinking aid, skin blemishes
8. stopper, big swallow
9. implement, stolen goods
10. precinct, illustrate

What are the ten word pairs?

Answer:

Camel Riddle

An Arab sheik is old and must will his fortune to one of his two sons. He makes a proposition. His two sons will ride their camels in a race, and whichever camel crosses the finish line LAST will win the fortune for its owner. During the race, the two brothers wander aimlessly for days, neither willing to cross the finish line. In desperation, they ask a wise man for advice. He tells them something; then the brothers leap onto the camels and charge toward the finish line. What did the wise man say?

Answer:

The rules of the race were that the owner of the camel that crosses the finish line last wins the fortune. The wise man simply told them to switch camels.

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