In a class, 55% of the students are boys. 60% of the boys and 80% of the girls love singing. What is the percentage of students who love sin

The answer is 42%.

55% of students are boys

45% of students are girls

60% x 55% ==33% of boys love singing

80% x 45% ==36% of girls love singing

33%  +  36% ==69% of all students love singing.