4 、There is a natural number, it is a multiple of 5 and 7, and when divided by 3, the remainder is 1. The smallest natural number that satisfies these conditions is
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【Analysis】The smallest natural number that is a multiple of both 5 and 7 is 0, but it is a multiple of 3. The second smallest is 35, but it leaves a remainder of 2 when divided by 3. The third smallest is 70, which leaves a remainder of 1 when divided by 3, so the number we are looking for is 70.