The decimal 0.4 is a simple decimal number, no repeating digits are involved, which can be easily converted to a fraction.
Let's convert the decimal 0.4 into fraction step by step.
1. Write down the decimal divided by 1: 0.4/1.
2. Multiply both top and bottom by 10 for every number after the decimal point. Since there is one number after the decimal point, we multiply by 10 once which gives: 4/10.
3. Now, we simplify the fraction above. Both 4 and 10 are divisible by 2. Hence, dividing the numerator and the denominator by 2, we get: 2/5.
So, the fractional equivalent of the decimal 0.4 is 2/5.