Final answer:
To find the number of girls on the field trip, set up a proportion using the given ratio and the total number of students. Solve for the number of girls by multiplying both sides of the equation by 4/5. Round up to the nearest whole number to obtain the final answer.
Step-by-step explanation:
To find the number of girls on the field trip, we need to determine the number of boys and girls using the given ratio. Since the ratio of girls to boys is 5 to 4, we can set up a proportion.
Let x be the number of girls. The number of boys would then be 4x/5.
We can write the equation 5x/4 = 108, since the total number of students is 108.
Multiplying both sides of the equation by 4/5 will give us x = 108 * 4/5 = 86.4.
Since we can't have a fraction of a student, we round up to the nearest whole number.
Therefore, there are 87 girls on the field trip.