The smallest rational number by which 1/3 should be multiplied so that its decimal expansion terminates after one place of decimal, is

Let x = p/q be a rational number, such that the prime factorization of q is of the form 2n 5m, where n, m are non-negative integers. Then x has a decimal expansion which terminates.


So 1/3 should be multiplied by 3/10 so that it is in the form of 2n5m.

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