To find the fraction that represents the number of boys on the trip, we can start by determining the number of girls.
If 0.6 were girls, that means:
\[ \text{Number of girls} = 0.6 \times 100 = 60 \]
Since there were 100 children in total, the number of boys can be calculated as:
\[ \text{Number of boys} = 100 - 60 = 40 \]
Now, to express the number of boys as a fraction of the total number of children:
\[ \text{Fraction of boys} = \frac{40}{100} \]
This simplifies to:
\[ \frac{40}{100} = \frac{2}{5} \]
However, since the question asks for the fraction to represent the number of boys in the format provided in the options, the correct response is:
\( \frac{40}{100} \) which is represented in your list as:
40100
So, the answer is 40100.