the decimal expansion of the rational number 31/ 2^{2} _{*}5 will terminate after

^{m} * 5^{n} whose so ever power is greater like here in this question power of 2 is greater then the power of 5 therefore it will be 2

See

Now if a number is of type , where n is not a multiple of 2 or 5, then the number of digits after zero in this number will be either a and b, whichever is greater.

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