Question: A library has 7 rectangular tables and the remaining tables will be square tables. A rectangular table seats 10 pupils while a square table seats 4 pupils. How many square tables are needed so that 90 pupils can read at the same time? Think carefully first, then make a decision:
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The rectangular tables seat 7 * 10 = 70 pupils. The square tables will seat 90 - 70 = 20 pupils. The library needs 20 / 4 = 5 square tables. So the answer is 5.
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