Working systematically

problem
Pasta timing

Age

7 to 11

Challenge level

Nina must cook some pasta for 15 minutes but she only has a 7-minute sand-timer and an 11-minute sand-timer. How can she use these timers to measure exactly 15 minutes?
problem
Knight's swap

Age

7 to 11

Challenge level

Swap the stars with the moons, using only knights' moves (as on a chess board). What is the smallest number of moves possible?
problem
Read this page

Age

11 to 14

Challenge level

Replace the letters with numbers to make the addition work out correctly. R E A D + T H I S = P A G E
problem
Map folding

Age

7 to 11

Challenge level

Take a rectangle of paper and fold it in half, and half again, to make four smaller rectangles. How many different ways can you fold it up?
problem
Egyptian rope

Age

7 to 11

Challenge level

The ancient Egyptians were said to make right-angled triangles using a rope with twelve equal sections divided by knots. What other triangles could you make if you had a rope like this?
problem
How many times?

Age

7 to 11

Challenge level

On a digital 24 hour clock, at certain times, all the digits are consecutive. How many times like this are there between midnight and 7 a.m.?
problem
Watch the clock

Age

7 to 11

Challenge level

During the third hour after midnight the hands on a clock point in the same direction (so one hand is over the top of the other). At what time, to the nearest second, does this happen?
problem
Calendar cubes

Age

7 to 11

Challenge level

Make a pair of cubes that can be moved to show all the days of the month from the 1st to the 31st.
problem
Team scream

Age

7 to 11

Challenge level

Seven friends went to a fun fair with lots of scary rides. They decided to pair up for rides until each friend had ridden once with each of the others. What was the total number rides?
problem
Seating arrangements

Age

7 to 11

Challenge level

Sitting around a table are three girls and three boys. Use the clues to work out were each person is sitting.