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Page last updated at 06:03 GMT, Thursday, 14 August 2008 07:03 UK
Maths made interesting

Can maths be fun?

Maths has long been associated with difficult school lessons and dreary household calculations, but for Rob Eastaway, author of How Many Socks Make a Pair, this does not have to be the case. See if you can answer his surprisingly interesting maths puzzles.

Maths the old fashioned way

1.) Question 1

You have a drawer in your bedroom that contains an assortment of black, blue and brown socks. You start randomly taking individual socks out of the drawer, but it's too dark to see what colour socks you have taken. How many socks do you need to take out in order to guarantee that you have got a matching pair?

Sock hanging contest
  1. 2
  2. 3
  3. 4
  4. All but two of the socks in the drawer

2.) Question 2

You are standing in front of the bathroom mirror and can see down to your navel. You walk back from the mirror. Can you now see:

Mirror
  1. Less of yourself
  2. The same amount
  3. More of yourself

3.) Question 3

You are at a wedding with 50 guests. What is the chance that among those guests there are at least two who share a birthday?

Steptoe and son
  1. Almost certain
  2. About 50-50
  3. About 1 in 7
  4. Extremely unlikely

4.) Question 4

Imagine a piece of string has been tied tightly around the earth's equator (assume the earth is a perfect sphere!), with thousands of children stationed around the earth next to the string. You now cut the string at one place, and add in one more metre of string to give it a little 'slack'. By how much can the children around the equator now lift up the string?

  1. Not quite enough to squeeze a razor blade under
  2. Enough to all simultaneously squeeze their hands under
  3. Enough for them to put their fists under
  4. Enough for them all to crawl under

5.) Question 5

You are listening to a random news story on the Today programme, which quotes some statistic, such as the number of refugees from a country, a company's profits, or the number of seconds it took a competitor to win a race. What is the chance that the first digit of the statistic is either a 1 or a 2 ?

  1. Almost certain
  2. About 50-50
  3. About 2/9 (22%), since the digit is equally likely to be a 1, 2, 3, 4, 5, 6, 7, 8 or 9
  4. Impossible to answer, it depends on the story.

6.) Question 6

A man leaves his tent. He walks 1 mile south. Then he walks 1 mile east. Then he walks one mile north. To his surprise, he now discovers that he is back at his tent, and at this moment he spots a bear. What colour is it?

Bear
  1. Black
  2. Brown
  3. White
  4. Pudsey

Answers

  1. Four socks. Taking out one more than the number of colours of sock in the drawer guarantees at least one pair.
  2. The same amount - as long as the mirror is vertical.
  3. Astonishingly, the chance of at least one birthday coincidence in a group of 50 people is about 98%.
  4. Adding one metre to the string increases the radius of the string circle around the earth by about 16cm, enough for a child to crawl under.
  5. Most statistics quoted in the news reliably follow 'Benford's Law' which says that roughly 50% of statistics begin with a 1 or a 2, while less than 10% begin with an 8 or a 9. There are exceptions, the main ones being people's ages and percentages.
  6. The bear has to be a polar bear because the only place where the walk returns to the starting point - and you might see a white bear - is the North Pole.

How did you do?

0 - 1 : Eaten by a polar bear

2 - 3 : Trapped on the equator

4 - 6 : Clean pair of socks




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