In a class of 90 students, the ratio of boys to girls is 7 to 8. How many boys are there in the class?

Explanation

Let the common multiplier be x. Since the ratio of boys to girls is 7:8, the total students can be expressed as 7x + 8x = 15x. Given that the total number of students is 90, we have 15x = 90, which gives x = 6. Therefore, the number of boys is 7x = 7 × 6 = 42.