Can you make a hypothesis to explain these ancient numbers?
In the Bag
Age 11 to 14 Challenge Level:
Ten marbles of varying colours are chosen at random and placed in a
bag. Can you guess the colours of the
10 marbles in the bag?
To help you make accurate predictions you can choose to see the
results of 10 viewings - each viewing removes a marble out of the
bag, records its colour and returns it to the bag before repeating the
You can choose to have as many viewings as you like before deciding
to "Make a Guess".
Each Round concludes when you have made a guess.
Can you reach a score of 1000
You start with 500 points. Each run of 10 viewings "costs" you 10
points but you can "earn" points by predicting accurately the
contents of the bag:
150 points for a perfect match 100 points for 9 matching
marbles 0 points for 8 matching
marbles -100 points for 7 or fewer
Can you develop an effective strategy for reaching 1000
Can you develop an effective strategy for reaching 1000 points in
the least number of rounds?
The NRICH Project aims to enrich the mathematical experiences of all learners. To support this aim, members of the
NRICH team work in a wide range of capacities, including providing professional development for teachers wishing to
embed rich mathematical tasks into everyday classroom practice.