The ratio of boys to girls in Ella’s grade is 3 to 4. The ratio of boys to girls in Minh’s grade is 4 to 5. Each grade has a total of 20 girls.

Answer 1

3/(3+4) = 3/7 x 20 = 60/7 = approximately 8.57 = about 9 boys in Ella's grade and 11 girls

4/(4+5) = 4/9 x 20 = 80/9 = approximately 8.89 = about 9 boys in Minh's grade and 11 girls

rounding to nearest integer. Assuming no fractional boys or girls.