In a math class, 9 pupils receive a grade of 90. If 18% of the class got 90, how many pupils are there in a class?

Let the total number of pupil be x.

Given that,

Number of pupils that received a grade of 90=9

Percentage of pupil that receive a grade of 90=18%

So,

18% of x=9

18x/100=9

x=50

Hence, there are 50 pupils in the class.

4 and 5)16.97 or 12√2

6)15.59 or 9√3

7)y = 15.59 or 9√3     x =27

8)17.80