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'In the Bag' printed from http://nrich.maths.org/

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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 process.

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.

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Can you reach a score of 1000 points?

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 matching marbles.

Can you develop an effective strategy for reaching 1000 points?
Can you develop an effective strategy for reaching 1000 points in the least number of rounds?

Describe your strategies.