Final answer:
The class of 90 students has 40 boys and 50 girls, as determined by applying the ratio of 4:5.
Step-by-step explanation:
The question is asking to find the number of boys and girls in a class of 90 students, given the ratio of boys to girls is 4:5. First, we combine the parts of the ratio 4+5 to get the total number of parts, which is 9. We then divide the total number of students by the total number of parts to find out how many students represent one part of the ratio: 90 students ÷ 9 parts = 10 students per part. Now, we multiply the number of parts for boys and girls by the number of students per part. For boys (4 parts): 4 × 10 = 40 boys. For girls (5 parts): 5 × 10 = 50 girls.