BECE Mathematics 2018 Paper

Concept:A ratio compares parts of a whole. If the ratio is $3:2$, then girls form $2$ parts out of the total $3 + 2 = 5$ parts.Explanation:Let the total number of students be $x$.Ratio of boys to girls is $3:2$.Sum of the ratio parts is $3 + 2 = 5$.Therefore, girls make up $\frac{2}{5}$ of the total students.Since the number of girls is $420$, we write:$\frac{2}{5} \times x = 420$Multiply both sides by $5$:$2x = 420 \times 5 = 2100$Divide both sides by $2$:$x = \frac{2100}{2} = 1050$Thus, the total number of students in the school is $1050$.Answer:$\boxed{1050}$ students, which is option A.