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playing-with-numbers!1
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playing-with-numbers!2
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separation-of-substances!1
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playing-with-numbers!3
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temperatureconversions!1
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natural-resources!1
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natural-resources!2
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soil-our-life!1
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electici-crcuit-and-electric-switch!1
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electici-crcuit-and-electric-switch!2
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electici-crcuit-and-electric-switch!3
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electici-crcuit-and-electric-switch!4
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magnetic-and-non-magnetic!1
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force-can-change-shape-of-an-object!2
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non-contact-force!1
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how-does-air-get-polluted-k1!1
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electronic-force!1