Question

72% of 25 students are good in mathamatics . how many are not good in mathematics

Answer 1

no. of students good in mathematics= 72/100 x 25= 18 students
no. of students not good in mathematics= 25- 18 = 7 students

∴ 7 students  are not good in mathematics

Answer 2

Total Students = 25

Out of these 25 students, percentage of the students who are interested in mathematics = 72% .

It means : 72% of 25

$\frac{72}{100} \times 25 = 18$

= 18 students are interested in mathematics.

Then , the questionnaire has asked about the number of students who are not interested in mathematics.

So , subtract 18 from the total strength.

= 25 -18 = 7

So, the required number of students is 7.