For the funfair, the school organizers ordered 30 rolls of tickets. Each roll of tickets has 100 tickets. The 4th graders bought 30% of the tickets while the 5th graders bought 50% of the remaining tickets. Then the 6th graders bought a total of 100 tickets. How many tickets were left unsold? Let's think first. Chain of thought:
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There were a total of 30 x 100 = 3000 tickets ordered by the school organizers. The 4th graders bought 3000 x 30 / 100 = 900 tickets. So, there were 3000 - 900 = 2100 tickets left for the other two grade levels. The 5th graders bought 2100 x 50 / 100 = 1050 tickets. So, 2100 - 1050 = 1050 tickets were left then. Since 100 tickets were bought by the 6th graders, therefore 1050 - 100 = 950 tickets were left unsold.
Therefore, the answer is 950.
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