List

Tales of the unexpected

When working on mathematical tasks, you may sometimes discover unexpected results that take you by surprise. In this feature, we have chosen some problems that we hope will astonish and amaze you.

 

Subtraction Surprise
problem

Subtraction surprise

Age
7 to 14
Challenge level
filled star empty star empty star

Try out these calculations. Are you surprised by the results?

Legs Eleven
problem

Legs eleven

Age
11 to 14
Challenge level
filled star filled star empty star

Take any four digit number. Move the first digit to the end and move the rest along. Now add your two numbers. Did you get a multiple of 11?

Angles inside
problem

Angles inside

Age
11 to 14
Challenge level
filled star empty star empty star

Draw some angles inside a rectangle. What do you notice? Can you prove it?

Triangle in a Triangle
problem

Triangle in a triangle

Age
14 to 16
Challenge level
filled star filled star empty star

Can you work out the fraction of the original triangle that is covered by the inner triangle?

Areas and Ratios
problem

Areas and ratios

Age
16 to 18
Challenge level
filled star filled star empty star

Do you have enough information to work out the area of the shaded quadrilateral?

Another Triangle in a Triangle
problem

Another triangle in a triangle

Age
16 to 18
Challenge level
filled star filled star empty star

Can you work out the fraction of the original triangle that is covered by the green triangle?