Mathematics · pattern A, Numeric fields
Enter a numerator and denominator for the decimal value, and find out whether it terminates — which depends entirely on the prime factors of the denominator.
divide the numerator by the denominator
A fraction in lowest terms terminates if and only if its denominator's only prime factors are 2 and 5. Anything else recurs forever.
0.3750000000
Ten factorises as 2 × 5, so a denominator built only from those primes divides some power of ten exactly and the decimal stops. A factor of 3 or 7 never does, which is why a third recurs and an eighth does not. In base 3 the situation would be reversed.
If the number is not the part you are stuck on, that is what the service is for — a specialist who explains the working, not just the answer.
Arithmetic runs in double-precision floating point, so results beyond about fifteen significant figures are not exact. Where a question wants an exact fraction or surd, keep the exact form rather than a decimal.