question_answer 1)

There are 20 girls and 15 boys in a class. (a) What is the ratio of number of girls to the number of boys? (b) What is the ratio of number of girls to the total number of students in the class?                

Answer:

                Given, number of girls = 20 and number of boys = 15 \[\therefore \] Total number of students in the class \[=20+15=35\] Ratio of number of girls to the number of boys \[\text{=}\frac{\text{Number}\,\text{of}\,\text{girls}}{\text{Number}\,\text{of}\,\text{boys}}\text{=}\frac{\text{20}}{\text{15}}\] \[=\frac{20\div 5}{15\div 5}=\frac{4}{5}=4:3\] [\[\because \] HCF of 20 and 35 = 5] (b) Ratio of number of girls to the total number of students in the class \[\text{=}\frac{\text{Number}\,\text{of}\,\text{girls}}{\text{Total}\,\text{number}\,\text{of}\,\text{students}}\text{=}\frac{\text{20}}{\text{35}}\] \[=\frac{20\div 5}{35\div 5}=\frac{4}{7}=4:7\] [\[\because \] HCF of 20 and 35 = 5]