# Teacher Birthday Feature

To celebrate NRICH's 20th birthday we have selected some 'hidden gems' to share with you.

We have chosen some tasks which you may not have come across before, perhaps because they are not so closely linked to the curriculum, perhaps because they have not been featured recently on the website or perhaps because they are relatively new. However, all of them are rich mathematical activities which will intrigue your learners and encourage them to think mathematically.  To find out more about the reasons for selecting each one, take a look at the article below.

We hope you enjoy exploring.

### Hidden Gems: Tasks to Celebrate Our 20th Birthday

##### Age 5 to 11
This article for primary teachers outlines the reasons for us selecting the tasks in our Hidden Gems Feature.

### Always, Sometimes or Never? KS1

##### Age 5 to 7Challenge Level
Are these statements relating to calculation and properties of shapes always true, sometimes true or never true?

### Animated Triangles

##### Age 5 to 7Challenge Level
Watch this "Notes on a Triangle" film. Can you recreate parts of the film using cut-out triangles?

### That Number Square!

##### Age 5 to 11Challenge Level
How quickly can you put back the numbers on the hundred square? What's the smartest way to do it?

### Up and Down Staircases

##### Age 7 to 11Challenge Level
One block is needed to make an up-and-down staircase, with one step up and one step down. How many blocks would be needed to build an up-and-down staircase with 5 steps up and 5 steps down?

### Always, Sometimes or Never? Shape

##### Age 7 to 11Challenge Level
Are these statements always true, sometimes true or never true?

### Ice Cream

##### Age 7 to 11Challenge Level
You cannot choose a selection of ice cream flavours that includes totally what someone has already chosen. Have a go and find all the different ways in which seven children can have ice cream.