Two or Three

There are 5 counters in a bag. Three are Argentinean (blue) and two are Brazilian (green). Three counters are randomly picked out of the bag, one by one. They are not returned to the bag.

 

 

What probability is higher?

A. The probability of choosing three Argentinean counters in a row.

B. The probability of choosing two Brazilian counters in a row and then one Argentinean counter.

Find the answer.

Chance for a Would-be Bride

There was a tradition in old Russia. A would-be bride gathers six long pieces of straw and grasp them in her hand. She then randomly ties pairs of knots on the top and the bottom. Since there are six blades of grass sticking out above and below the hand, she will tie three knots on the top and three knots on the bottom. If she forms one big ring, she gets married soon.

Estimate the probability that the girl will get married soon.

The problem is mentioned in The New York Times NUMBERPLAY and it is credited to Sunil Singh.

Answer

Secret Agent 007

Seven secret agents are on payroll of a government.

Secret agent 001 spies on a secret agent who spies on secret agent 002,

who spies on a secret agent who spies on secret agent 003,

who spies on . . . spies on secret agent 007

who spies on a secret agent who spies on secret agent 001.  

Who spies on secret agent 007?

Answer

 

Counting Pets

Gerry has several pets at home.

All of them are dogs, except for three.

All of them are cats, except for four.

All of them are tortoises, except for five.

How many dogs does he have?

 

Aplusclick Best Puzzles 2019

These are the Best Puzzles published at www.aplusclick.org in 2019.

 

Aplusclick Best Puzzles 2019 from Igor Kokcharov, Ph.D, PMP

Motorway Problem

How to choose the shortest road that connects several towns. This is a story about local and global minimums. Excellent presentation  of soapy films.

Sign Logic Puzzle

Find a mistake. Think differently!

 

Find more logic puzzles for all ages in Think Outside the Box collection of puzzles.

Big Ben Maths

Big Ben is the nickname for the Great Bell of the clock at the north end of the Palace of Westminster in London, United Kingdom.  

A pile of old coins helps to keep the clock mechanism accurate.  The pennies are stacked on the pendulum of the clock and have acted as weights. Adding or taking away coins effects the pendulum’s centre of mass and the rate at which it swings. A single penny will change the clock’s speed by two fifths of one second per day.

How does the weekly time change if we add 5 pennies to the pendulum?

Answer

At twelve o’clock, twelve chimes  ring from the great bell in 44 seconds. ## How long does it takes to ring the hours at 15:00 ?

Answer

18 Best Aplusclick Puzzles of 2018

New challenges:

What is the easiest way to make it correct?            Answer

In what Olympic sport does the winner cross the line facing backwards?      Answer

What time is it?         Answer

What is the necessary mirror size?     Answer

Find all 18 best puzzles at

18 Aplusclick Puzzles 2018 from Igor Kokcharov, Ph.D, PMP

Interesting Maths Facts

 

• Notches (cuts or indentation) on animal bones prove that humans have been doing mathematics since around 30,000 BC.
• Ancient Greeks used little rocks to represent numbers. The name of Calculus means pebbles in Greek.
• The = sign (“equals sign”) was invented by 16th Century Welsh mathematician Robert Recorde, who was fed up with writing “is equal to” in his equations.
• The word hundred is derived from the word “hundrath”, which actually means 120 and not 100.
• Zero (0) is the only number which cannot be represented by Roman numerals.
• Many Chinese hospitals do not have a 4th floor  because the words four in Japanese, Cantonese, Mandarin and Korean (shi, sei, si, sa) sound the same as the words in those languages for death.
• Forty is the only number with letters in alphabetical order, while one is the only one with letters in reverse order.
• The number 5 is pronounced as ‘Ha‘ in Thai language. 555 is also used by some as slang for ‘HaHaHa’.
• Zero is an even number. Mathematicians remember it. Many people take longer to decide whether it is even or odd.