R = 24.84 ÷ (3. 14x2+2) = 3cm。

S=3. 14x3x3=28.26 cm2。

2、

Use 750-420=330 kg.

Flour delivered (330-750x1/3) ÷ (60%-1/3) = 300kg.

3、

The original weight of reactor B is 95÷(4+3x25%)x4=80 tons.

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