question_answer 3)

                72% of 25 students are good in mathematics. How many are not good in Mathematics?

Answer:

                Total number of students = 25 Students good in mathematics = 72%  \[\therefore \] Students who are not good mathematics = 100% ? 72% = 28% \[\therefore \] Number of those students who are not good in mathematics = 28% of 25 \[=\frac{28}{100}\,\times 25=7\] Hence, 7 students are not good in mathematics.