Advertisement

We need your help now

Support from readers like you keeps The Journal open.

You are visiting us because we have something you value. Independent, unbiased news that tells the truth. Advertising revenue goes some way to support our mission, but this year it has not been enough.

If you've seen value in our reporting, please contribute what you can, so we can continue to produce accurate and meaningful journalism. For everyone who needs it.

Shutterstock/Ruth Black

Maths Week: Your Saturday puzzle

Fancy a mathematics challenge?

MATHS WEEK STARTS today and, as is our annual tradition, we’re setting our readers some puzzles. Give them a go!

Day One – A Birthday Match

The Irish rugby squad has two players who share a birthday. What are the chances of that?

This is known as the Birthday Paradox as the answer is quite surprising – largely because our brains aren’t well evolved to assess probabilities. Probability itself is a relatively recent branch of maths dating back to the 17th Century (more about this later in the week).

How many people would we have to have in a room to have a 100% chance of two people sharing a birthday?

There are 365 days in a year, or 366 in a leap year. Therefore, we could have 366 people in a room who all have different birthdays. If one more person walked into the room, we would have to have a birthday match. That is 367 people to be 100% sure of having at least one matching birthday.

A much more difficult question is, how many people would we have to have in a room to have a 50:50 chance of two people sharing a birthday? So, if 367 are needed to be 100% certain of a matching birthday, might we need half of that number to have a 50% chance? Would that be 183 people?

The answer is rather surprising at 23 people. One of the reasons we find it surprising is that we might be thinking of ourselves and the chance of somebody sharing a birthday with us. The chance of a person walking into a room of 22 other people and finding a birthday that matches their own is much smaller and is about 6%. In a typical school with an average class size of 25 pupils you would expect around half the classes to contain a matching birthday.

In the Irish rugby squad, there are 33 players and the probability of finding a matching birthday is a little over 75%. The probability in the starting 15 would be around a 25%, but it just happens that the two players sharing a birthday are named in the starting line-up today and they are Peter O’Mahony and Dan Sheehan who blow out the candles on 17 September each year.

Each day, for Maths Week, The Journal will be bringing you fun puzzles. For many of these, we’ll be drawing on classic puzzles where today’s one comes from 1963 and the pen of the legendary recreational maths author, Martin Gardner.

So, here we go:

When I asked her how old she was, she smiled and said cryptically, “The day before yesterday I was 22, but next year I’ll be 25.”

Can you explain how this could be?

Come back tomorrow at 7.30pm for the answers to today’s puzzle. 

The puzzles this week have been compiled by Eoin Gill and Colm Mulcahy of Maths Week Ireland / South-East Technological University (SETU). 

Readers like you are keeping these stories free for everyone...
A mix of advertising and supporting contributions helps keep paywalls away from valuable information like this article. Over 5,000 readers like you have already stepped up and support us with a monthly payment or a once-off donation.

Close
9 Comments
This is YOUR comments community. Stay civil, stay constructive, stay on topic. Please familiarise yourself with our comments policy here before taking part.
Leave a Comment
    Install the app to use these features.
    Mute De Wit
    Favourite De Wit
    Report
    Jan 1st 2015, 7:04 PM

    Russia tried to warn the west they were backing the wrong horse, they didn’t listen…

    87
    Install the app to use these features.
    Mute amos brearly
    Favourite amos brearly
    Report
    Jan 1st 2015, 7:10 PM

    And what is the UN doing? Nothing, just like they watched Yugoslavia go into meltdown.

    83
    Install the app to use these features.
    Mute William Boyd
    Favourite William Boyd
    Report
    Jan 2nd 2015, 2:11 AM

    When a religion is involved particularly Islam, evil will out, even simple brain movements are swamped by brainwashing

    5
    Install the app to use these features.
    Mute Bertie
    Favourite Bertie
    Report
    Jan 1st 2015, 7:17 PM

    All because the USA armed, trained and funded rebels who wanted to overthrow the democratically elected government. Good old Murikka.

    56
    Install the app to use these features.
    Mute Avina Laaf
    Favourite Avina Laaf
    Report
    Jan 1st 2015, 7:54 PM

    Whatever else about the clusterfvck that is present-day Syria, don’t be under the illusion that Assad was ever democratically elected.

    48
    Install the app to use these features.
    Mute x
    Favourite x
    Report
    Jan 1st 2015, 8:05 PM

    Democratically elected? Assad has been in power for 15 years and his father 29 years before that both winning rigged/unopposed elections

    42
    See 16 more replies ▾
    Install the app to use these features.
    Mute Ben Murphy
    Favourite Ben Murphy
    Report
    Jan 1st 2015, 8:09 PM

    That was his point.

    5
    Install the app to use these features.
    Mute Avina Laaf
    Favourite Avina Laaf
    Report
    Jan 1st 2015, 8:12 PM

    Ben, open elections haven’t been held in Syria for over 40 years. All candidates in any so-called elections have to be pre-approved by the regime – hardly what anyone would call democratic.

    24
    Install the app to use these features.
    Mute Declan Noonan
    Favourite Declan Noonan
    Report
    Jan 1st 2015, 8:20 PM

    Bertie, would you like to talk about the uprising that assads father brutally put down in 1982? This is the same situation over again.

    19
    Install the app to use these features.
    Mute Frank
    Favourite Frank
    Report
    Jan 1st 2015, 8:25 PM

    Avina Laaf_ Assad ( like Saddam Hussein) protected vulnerable ancient Christian settlements from US backed head hackers.

    20
    Install the app to use these features.
    Mute Horgay H
    Favourite Horgay H
    Report
    Jan 1st 2015, 8:28 PM

    Re Avina

    Brush up on your history. Elections were held recently enough in Syria. I believe it was over a year ago at this stage.

    Also, don’t forget NATO’s own polls a few months back put support for Assad at at least 70% of the population and even up to 85/90%.

    Syria could not have fought off the proxy invasion of its country by Saudi Arabia/Qatar/Turkey/UK/France/US etc without the full support of its population, which it has had. It was very telling early in the conflict and middle that whenever the ‘rebels’ entered an area and took it over the civilian population fled en masse. Whenever the ‘rebels’ were defeated the civilian population returned.

    Besides, we cannot talk of democracy and elections. On the ladder of democracies, ours surely must be on the bottom. Elections every couple of years, very low vote turnout and then our elected representatives go off and give their full support to the likes of the FSA at the start of the Syrian invasion. The FSA has said from the outset that Syria would become an Islamic state with Sharia law if it ever succeeded with its invasion. I do not want my dim-witted elected representatives supporting the likes of that.

    18
    Install the app to use these features.
    Mute Horgay H
    Favourite Horgay H
    Report
    Jan 1st 2015, 8:31 PM

    Re Declan.

    You haven’t a leg to stand on. You fervently support the US on nearly every issue yet how many democratically ejected governments has the US toppled because they didn’t suit it’s geopolitical desires. The answer. Countless. Give William Blum a read.

    17
    Install the app to use these features.
    Mute Frank
    Favourite Frank
    Report
    Jan 1st 2015, 8:34 PM

    Bassar Al Assad must be commended for single handily taking on the evil proxy terrorist forces of the West.

    http://s10.postimg.org/sw3ji1zmh/assad_1.jpg

    17
    Install the app to use these features.
    Mute Horgay H
    Favourite Horgay H
    Report
    Jan 1st 2015, 8:37 PM

    Re Frank

    I agree. He is a modern day hero to the people of Syria. I admire his stern belief on his duty to protect his country.

    12
    Install the app to use these features.
    Mute Avina Laaf
    Favourite Avina Laaf
    Report
    Jan 1st 2015, 8:37 PM

    Frank, would you like to comment on Saddam Hussein’s treatment of the Kurds or the Marsh Arabs? Or maybe Assad senior’s treatment of the civilians of Hama?

    15
    Install the app to use these features.
    Mute Avina Laaf
    Favourite Avina Laaf
    Report
    Jan 1st 2015, 8:44 PM

    Horgay, funnily enough civilians tend to flee conflict zones whenever possible, and return when peace returns – nothing odd or telling about that. Regular journal readers will know you have your own take on events in Syria (to which you’re perfectly entitled of course). Most others who have been following this conflict from the very early stages (before your loathed ‘mainstream media’ even began to take an interest in fact) realise that the reality is much more complex than your version however.

    11
    Install the app to use these features.
    Mute Avina Laaf
    Favourite Avina Laaf
    Report
    Jan 1st 2015, 8:49 PM

    Horgay, please tell me how indiscriminately dropping barrel bombs on built-up areas packed full of innocent civilians is ‘protecting’ his people? The fact that you find these sorts of actions worthy of admiration is nauseating.

    13
    Install the app to use these features.
    Mute Frank
    Favourite Frank
    Report
    Jan 1st 2015, 8:52 PM

    Avina Laaf_ The combined slaughter caused on the Kurds. Marsh Arabs and Civilians of Hama would dwarf that of what the United States has caused in the Middle East.

    What makes matters more unbearable is that these ongoing atrocities are carried out by proxy terrorists armed and trained by the US. Example would be those schoolchildren blasted to pieces last October by “moderate” rebels.

    This shows up the true yellow bellied nature of the United States Government,

    11
    Install the app to use these features.
    Mute Avina Laaf
    Favourite Avina Laaf
    Report
    Jan 1st 2015, 9:00 PM

    Even if what you say is true Frank, surely you can’t say that one justifies the other, or in your mind are christian lives worth more than other lives??

    8
    Install the app to use these features.
    Mute Horgay H
    Favourite Horgay H
    Report
    Jan 1st 2015, 9:03 PM

    Re Avina

    I have been commenting on the Syrian conflict since its inception, but under a different guise. And I tell you what, the majority of what I said was ridiculed by you and others when I said the West was arming and training foreign Islamic jihadists in Turkey and sending them into Syria to cause mayhem and destabilise the country.

    You have gotten Syria competition wrong. I guess it hurts when the recent ex US Ambassador to Turkey mucks up and says exactly that.

    11
    Install the app to use these features.
    Mute Kustin J Crush
    Favourite Kustin J Crush
    Report
    Jan 1st 2015, 9:40 PM

    @ Horgay/Frank…. sure Aasad is a lovely chappie, take some more of the meds . ( and no! Some of the other mob are as bad if not worse!…… mind you you won’t hear much condemnation from our chatting classes (no Israelis involved, don’t you know!!!!)

    5
    Install the app to use these features.
    Mute Frank
    Favourite Frank
    Report
    Jan 1st 2015, 10:37 PM

    Kustin J Crush_ At least Bassar Assad doesn’t cheer lead a nation that slaughters 500+ defenseless children.

    5
    Install the app to use these features.
    Mute KeiKe
    Favourite KeiKe
    Report
    Jan 1st 2015, 7:41 PM

    The representations of the UN in the Team America movie….still pretty accurate

    14
    Install the app to use these features.
    Mute Horgay H
    Favourite Horgay H
    Report
    Jan 1st 2015, 8:15 PM

    The article is a fine piece of propaganda and a further attempt to frame the narrative of the story.

    For all those out there who do not follow world affairs then you need to know the following.

    The conflict did not give rise to Islamic groups, Islamic groups were sent into Syria from Turkey from the outset after being armed and trained by the West there. They then proceeded to attack Syrian state forces and begun an ethnic cleansing of areas they began to control, eliminating thousands upon thousands of Christians and other groups. They proceeded to wreck civilian infrastructure, cut communications and killed government employees from postmen to nurses en masse. This was all done with the full knowledge of the moral West. Innocent civilians would not get in the way if geopolitical goals. The ‘uprising’ ( http://thebricspost.com/an-eyewitness-to-the-syrian-rebellion-father-frans-in-his-own-words/#.VKWqYnanw0M) began a few days after a gas pipe deal was signed which was not favourable to Qatar.

    Don’t let the media in the West frame your views on world affairs. We, in the West, have a lot of blood on our hands. We elect these maniac, evil politicians who have let these crimes be committed.

    The summary of the Syrian conflict cannot be whitewashed. The media has covered up the meddlings of the West so many times from Rwanda to Iraq to Libya to, now Ukraine and Syria.

    10
    Install the app to use these features.
    Mute Declan Noonan
    Favourite Declan Noonan
    Report
    Jan 1st 2015, 8:21 PM

    Horgay, no blood on my hands! Don’t think that you speak for anyone but your deluded self.

    9
    Install the app to use these features.
    Mute Horgay H
    Favourite Horgay H
    Report
    Jan 1st 2015, 8:35 PM

    Re Declan

    If you have voted for either the Democrats or Republicans then I am afraid there is. And plenty of it. They are two sides of the same coin, giving the illusion of choice.

    The foreign policy if the US has been directly responsible for the deaths of tens of millions of innocent mem, women and children. This cannot be dispute by any sane person. It still does. Look at the Congo, look at what the US help perpetrate in Rwanda with the genocide there that was the result of American meddling.

    9
    See 3 more replies ▾
    Install the app to use these features.
    Mute Petr Tarasov
    Favourite Petr Tarasov
    Report
    Jan 1st 2015, 10:31 PM

    Ah there’s Deco again, defending the indefensible.

    8
    Install the app to use these features.
    Mute Declan Noonan
    Favourite Declan Noonan
    Report
    Jan 1st 2015, 10:37 PM

    Petr, can you please tell me what I’m defending? How did you get “defending the indefensible” from my comment? Or are you taking my quote that I have used on Horgay? This is the guy who has defended dictators around the world. Surely you have noticed that. Or are you in bed with the likes of Horgay, Frank and others?

    4
    Install the app to use these features.
    Mute Frank
    Favourite Frank
    Report
    Jan 1st 2015, 11:06 PM

    Declan Noonan_ You are very confused of who you defend.

    Yesterday you admitted that you don’t support Syrian Moderate Rebels.

    Yet the regime that you constantly defend openly supports moderate Syrian Rebels.

    8
    Install the app to use these features.
    Mute Charles Mcdonald
    Favourite Charles Mcdonald
    Report
    Jan 1st 2015, 7:43 PM

    Almost 9 an hour.

    7
    Install the app to use these features.
    Mute Charles Mcdonald
    Favourite Charles Mcdonald
    Report
    Jan 1st 2015, 7:47 PM

    Or look at it this way by the time you read the article and comment there is another woman raped strangled or hanged. Maybe another man shot in face or head hacked off.

    I’m sure the Un will issue another very strongly worded letter and maybe have a meeting about having a meeting

    15
    Install the app to use these features.
    Mute Wasna Matkaw
    Favourite Wasna Matkaw
    Report
    Jan 1st 2015, 7:52 PM

    Let them get on with it.

    5
    Install the app to use these features.
    Mute Petr Tarasov
    Favourite Petr Tarasov
    Report
    Jan 1st 2015, 9:47 PM

    A disgusting comment.

    7
    Install the app to use these features.
    Mute Charles Mcdonald
    Favourite Charles Mcdonald
    Report
    Jan 1st 2015, 10:29 PM

    Truely horrible. Of this 9 an hour how many are children? I don’t know but I really don’t think 9 soldiers or militants. Talking about innocent men women and children. There was a video few weeks ago I think was on here showing a girl being condemned to stoning by her father. Another months ago of garroting women. Truely vile. Now let’s not be silly it’s not all assad there is war crimes on both sides.

    Arming moderates well who dedides who is a moderate ?? Throwing arms at these people invites trouble. If people rise up and it’s a good cause fine give them a fighting chance but not if their cause involves evil extremists

    8
    Install the app to use these features.
    Mute Windom Earle
    Favourite Windom Earle
    Report
    Jan 1st 2015, 7:28 PM

    Not 200,000 as they reported past time

    2
Submit a report
Please help us understand how this comment violates our community guidelines.
Thank you for the feedback
Your feedback has been sent to our team for review.

Leave a commentcancel

 
JournalTv
News in 60 seconds