   Question Answers

# $72\%$ of 25 students are good in mathematics. How many are not good at mathematics?  Hint: As we know that the total number of students is 25. And as the percentage of good students is known so we can calculate the percentage of students who are not good in mathematics using$(100 - good\% )$. Hence, we calculate the number of students who are not good in maths using the above number of percentage of those students who are not good in mathematics, by using the formula, $n\% of A = \dfrac{n}{{100}} \times A$

As we know that the percentage of good students is $72\%$ and in total there are 25 students.
So, the percentage students not good in mathematics are,
$= (100 - good\% ) \\ = (100 - 72)\% \\ = 28\% \\$
Hence, in order to calculate the number of students who are not good at maths, we need to calculate a total $28\%$of 25
students.
As, $n\% ofA = \dfrac{n}{{100}} \times A$, using this we get,
$\Rightarrow$ Number of students who are not good in maths$= \dfrac{{28}}{{100}} \times 25$
On simplification we get,
$\Rightarrow$Number of students who are not good in maths$= \dfrac{{28}}{4}$
On dividing 28 by 7 we get,
$\Rightarrow$Number of students who are not good in maths$= 7$
Hence, the total number of students not good in mathematics is 7.

Note: Using the concept of mathematics that if $x\% + y\% = 100\%$and so if the percentage of one is known we can calculate the quantity of another quantity.
As the percentage can be given by,
$\dfrac{{n(notgood)}}{{n(total)}} = \dfrac{x}{{100}}$
Hence, the total number of not good students in maths can also be calculated.
Thus, do the calculation properly without any mistake.
View Notes
Group Theory in Mathematics  Importance of Good Manners Essay for Students in English  Table of 72 - Multiplication Table of 72  CBSE Class 8 Maths Chapter 8 - Comparing Quantities Formulas  Table of 25 - Multiplication Table of 25    Status of Women in India Essay for Students in English  Importance of Sports Essay for Students in English  Table of 9 - Multiplication Table of 9  What are the Functions of the Human Skeletal System?  Important Questions for CBSE Class 7 English Honeycomb Chapter 9 - A Bicycle In Good Repair  Important Questions for CBSE Class 9 Maths Chapter 9 - Areas of Parallelograms and Triangles  Important Questions for CBSE Class 7 Maths Chapter 8 - Comparing Quantities  Important Questions for CBSE Class 10 Maths Chapter 9 - Some Applications of Trigonometry  Important Questions for CBSE Class 8 Maths Chapter 8 - Comparing Quantities  Important Questions for CBSE Class 9 Science Chapter 9 - Force and Laws of Motion  NCERT Books for Class 9 Maths Chapter 9  Important Questions for CBSE Class 9 Maths  Important Questions for CBSE Class 9 Maths Chapter 4 - Linear Equations in Two Variables  Important Questions for CBSE Class 9 Science Chapter 4 - Structure of The Atom  Previous Year Question Paper of CBSE Class 10 English  CBSE Class 12 Maths Question Paper 2020  CBSE Class 10 Maths Question Paper 2020  Maths Question Paper for CBSE Class 10 - 2011  Maths Question Paper for CBSE Class 10 - 2008  CBSE Class 10 Maths Question Paper 2017  Maths Question Paper for CBSE Class 10 - 2012  Maths Question Paper for CBSE Class 10 - 2009  Maths Question Paper for CBSE Class 10 - 2010  Maths Question Paper for CBSE Class 10 - 2007  RD Sharma Class 9 Solutions Chapter 25 - Probability (Ex 25.1) Exercise 25.1  RD Sharma Solutions for Class 9 Maths Chapter 25 - Probability  NCERT Solutions for Class 8 Maths Chapter 8 Comparing Quantities  NCERT Solutions for Class 7 Maths Chapter 8  RD Sharma Class 8 Solutions Chapter 25 - Pictorial Representation of Data As Pie Charts Or Circle Graphs (Ex 25.1) Exercise 25.1  RS Aggarwal Solutions Class 8 Chapter-25 Probability (Ex 25B) Exercise 25.2  RS Aggarwal Solutions Class 8 Chapter-25 Probability (Ex 25A) Exercise 25.1  RD Sharma Class 11 Solutions Chapter 25 - Parabola (Ex 25.1) Exercise 25.1  RD Sharma Class 7 Solutions Chapter 25 - Data Handling IV (Ex 25.1) Exercise 25.1  RD Sharma Class 12 Solutions Chapter 25 - Vector or Cross Product (Ex 25.1) Exercise 25.1  