Live Problems - Stage 4 & 5

Each time you visit the NRICH site there will be some activities which are 'live'. That means we are inviting you to send us your solutions and we will publish a selection of them, along with your name and school. If you'd like to read more about what we're looking for, read this short article.

Stage 4 & 5 Toughnutslive

Stage: 5 Challenge Level: Challenge Level:1

These Stage 4 and 5 problems haven't been solved yet. Can you be the first?

To Log or Not to Log?live

Stage: 5 Challenge Level: Challenge Level:1

Which of these logarithmic challenges can you solve?

Log Latticelive

Stage: 5 Challenge Level: Challenge Level:1

Can you figure out how each log fits into the lattice?

How Fast Does it Grow?live

Stage: 5 Challenge Level: Challenge Level:1

Exponential functions grow pretty quickly...

Reach for the Starslive

Stage: 5 Challenge Level: Challenge Level:1

Some graphs grow so quickly you can reach dizzy heights...

Matching Criminalslive

Stage: 4 and 5 Challenge Level: Challenge Level:3 Challenge Level:3 Challenge Level:3

DNA profiling is an invaluable tool for the police. However, when it comes to probability, things aren't always as straightforward as they seem.

The ELISA Testlive

Stage: 4 and 5 Challenge Level: Challenge Level:2 Challenge Level:2

In 1% of cases, an HIV test gives a positive result for someone who is HIV negative. How likely is it that someone who tests positive has HIV?