125 25 5 1 1/5 ____
The pattern observed in the given sequence is that each number is divided by 5 to obtain the next number. Applying this pattern, the next number in the sequence will be obtained by dividing the previous number (1/5) by 5.
1/5 ÷ 5 = 1/25
Therefore, the missing number in the sequence is 1/25.