Question

72% of 25 students are good in mathematics how many are not Good in mathematics?

Answer 1

there are total students = 100%
students good in maths = 72%
students not good in maths = 100% - 72%
= 28%
28% of 25
= 28× 25/100
= 7
so 7 students are not good in maths

Answer 2

take 4students as 1% (because 100/25=4)

then 72%are good in maths

so, no of students good in maths are 72/4

=18 students

7 students are not good in maths