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World Maths Day: Can you solve some of the most challenging problems around?

Numeracy charity says mathematical skills 'have got worse, not better' in the UK

Aftab Ali
Student Editor
Tuesday 13 October 2015 13:10

No doubt, you’ll have jumped out of bed this morning, ready and raring to celebrate – wait for it – World Maths Day (WMD), because we all know just how much Britons love to sink their teeth into a good mathematical problem.

If 2015 is anything to go by, the UK doesn’t have the world’s best mathematicians after Scottish pupils reacted with fury over a crocodile and zebra duo, followed by English and Welsh students falling out with a girl named Hannah over a conundrum with her sweets.

However, one global educational event is giving the nation the chance to redeem itself by rolling up its sleeves and delving into the world of puzzles and problems.

Organised by the World Education Games (WEG), the event is taking place from 13 to 15 October, with WMD bringing together students from across the globe in live competition with their peers.

Four online gaming modes are being made available, allowing participants to choose whether they want to challenge other international students, within their own school or class, or even warm up their skills against the computer.

According to National Numeracy – an independent charity established in 2012 to help raise low levels of numeracy among both adults and children – mathematical skills have gotten worse, not better, with roughly four in five adults affected across the UK, costing around £20bn to the country each year.

With even The Great British Bake Off finalist, Ian Cumming, adding how maths factored into his progress on the hit BBC show, why not have a go at some challenging, yet fun, problems, one of which – Cheryl’s birthday – had the world debating recently?:

1) Cheryl’s birthday

Albert and Bernard just become friends with Cheryl, and they want to know when her birthday is. Cheryl gives them a list of 10 possible dates:

May 15, May 16, May 19, June 17, June 18, July 14, July 16, August 14, August 15, and August 17

Cheryl then tells Albert and Bernard separately the month and the day of her birthday respectively.

Albert: I don’t know when Cheryl’s birthday is, but I know that Bernard does not know too.

Bernard: At first I don’t know when Cheryl’s birthday is, but I know now.

Albert: Then I also know when Cheryl's birthday is.

So when is Cheryl’s birthday?

See the solution here.

2) Crossing the bridge

Four people need to cross a rickety bridge at night. Unfortunately, they have only one torch and the bridge is too dangerous to cross without one. The bridge is only strong enough to support two people at a time. Not all people take the same time to cross the bridge. Times for each person: 1 minute, 2 minutes, 7 minutes, and 10 minutes. What is the shortest time needed for all four of them to cross the bridge?

See the solution here.

3) Probability of having boy

In a country where everyone wants a boy, each family continues having babies until they have a boy. After some time, what is the proportion of boys to girls in the country? (Assuming probability of having a boy or a girl is the same).

See the solution here.

4) Number magic

If you multiply me by 2, subtract 1, and read the reverse the result you’ll find me. Which numbers can I be?

See the solution here.

5) Sunday’s child

Recently, somebody said: “My grandfather was born on the first Sunday of the year. His seventh birthday was also on a Sunday.” In which year was said grandfather born?

See the solution here.

6) One bulb, three switches

You have three switches in a room. One of them is for a bulb in next room. You cannot see whether the bulb is on or off until you enter the room. What is the minimum number of times you need to go in to the room to determine which switch corresponds to the bulb in next room?

See the solution here.

7) School lockers

A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony:

There are one thousand lockers and one thousand students in the school. The principal asks the first student to go to every locker and open it. Then he has the second student go to every second locker and close it. The third goes to every third locker and, if it is closed, he opens it, and if it is open, he closes it. The fourth student does this to every fourth locker, and so on. After the process is completed with the thousandth student, how many lockers are open?

See the solution here.

8) One thousand monkeys

A very big building in which one thousand monkeys are living is lighted by one thousand lamps. Every lamp is connected to a unique on/off switch, which are numbered from 1 to 1000.

At some moment, all lamps are switched off. But because it is becoming darker, the monkeys would like to switch on the lights. They will do this in the following way:

Monkey 1 presses all switches that are a multiple of 1

Monkey 2 presses all switches that are a multiple of 2

Monkey 3 presses all switches that are a multiple of 3

Monkey 4 presses all switches that are a multiple of 4

Etc., etc.

How many lamps are switched on after monkey 1000 pressed his switches? And which lamps are switched on?

See the solution here.

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