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In order to solve the question and reach 1000 points in the least number of the round, you have to perform the random viewings twice. This will give you an insight into the different colours of the marble in the bag. For example, when you perform the random viewing first and you see there are 5 red marbles and in the second time, there are six red marbles. In this case, by guessing 5 marbles you are more likely to get the 150 points by guessing the colour of every marble which is the maximum amount in one round. Also in the same random viewing, for example you get no blue marbles and in the second random viewing, there is only one blue marble. You would guess none or one blue marble. By doing this you are more likely to get the points because if don't take any random viewing it is very likely you lose the points. Therefore, it is better to lose 20 points but by getting the data from the random viewing you are much more likely to get the 1000 points in a faster and more efficient way.
Overall, in order to solve the question, you have to take into account the data form the random viewing and use that to choose a suitable number of marbles of the colours explained above.