Puzzles

These puzzles are ideal for a fun way to start a lesson and get everybody's brains warmed up.

Stationery dilemma

A man bought some pens, pencils and paperclips at the following prices:
Pens         10p each
Pencils      5p each
Paperclips  1p for two

If the man bought a total of 100 items for a total cost of £1. How many of each item did he buy?

Lightbulb problem

In your cellar there are three light switches in the OFF position. Each switch controls 1 of 3 light bulbs on the floor above.
You may move any of the switches but you may only go upstairs to inspect the bulbs one time. How can you determine the switch for each bulb with only one
inspection?

The lazy Gardener

It takes two gardeners 8 days to mow a lawn. 
One is lazy and one is energetic.
The energetic one would only take 12 days to
mow it on his own. 
How many days would the lazy gardener take to
mow the lawn on his own?

Spiders

Three spiders named Mr Eight, Mr. Nine and Mr. Ten are crawling on the jungle floor. One spider has 8 legs; one spider has 9 legs; one spider has 10 legs.
  “I think it is quite interesting,” says Mr. Ten, “that none of us have the same number of legs that our names would suggest.”
  “Who cares?” replies the spider with 9
legs.
 
How many legs does Mr. Nine have?

An old friend

A woman was walking down the street when she ran into an old friend whom she hadn’t seen since school.
 ‘Hello, I haven’t seen you for twenty years,’ she said. ‘How are you?’
 ‘Well I got married ten years ago, and this is our son,’ was the response.
 ‘Hello,’ said the woman to the boy,‘and what is your name?’
 ‘It’s the same as Daddy’s.’
 ‘Ah, then it’s Michael,’ said the woman.
How could she have known this when the boy’s name has not been mentioned?

Number magic

Pick a number (a whole number will be easier, but it doesn't have to be)
Add 5
Double your answer
Add 20
Halve you answer
Now minus the number you started with

What is your answer?
Try it again with another number

Notebook problem

If six boys can fill up six notebooks in six weeks and four girls can fill up four notebooks in four weeks, how many notebooks can a class of twelve boys and twelve girls fill up in twelve weeks?
 

Toasting problem

You want to make 3 slices of toast under the grill.
Your grill will only take 2 slices at the same time and only toasts one side at a time.
Assuming it takes 30 seconds to toast one side and moving a slice takes no time at all, how quickly can you toast all three slices on both sides?

Hint: It takes less than 120 seconds.
Check out this article on ideas for maths lesson starters.

The fastest man on Earth

In 2005, Asafa Powell of Jamaica was dubbed the fastest man on Earth after running the 100 metres in 9.77 seconds.

At the time, the record for the 200 metres was 19.32 seconds set by Michael Johnson.

Who had the fastest average speed?

(Work it out in metres per second)