Integers, Rational Numbers And Real Numbers

Integers: These are whole numbers, including positive numbers, negative numbers, and zero. Examples: $-3$, $0$, $7$.

Rational Numbers: These are numbers that can be expressed as fractions, where the numerator and denominator are both integers. Examples: $\displaystyle\frac{3}{4}$​, $\displaystyle-\frac{2}{5}$, $0.25$ (which is $\displaystyle\frac{1}{4}$​ in fraction form).

Real Numbers: This includes all rational numbers and irrational numbers. Rational numbers can be expressed as fractions or decimals, while irrational numbers cannot be expressed as fractions and have non-repeating, non-terminating decimal expansions. Examples: $\large\pi$ (irrational), $\sqrt{2}$ (irrational), $1.5$ (rational).

In this chapter, we will be discussing the below-mentioned topics in detail

• Proper Fractions, Improper Fractions, Mixed Numbers
• Adding and subtracting fractions and mixed numbers 
• Adding and subtracting negative fractions and mixed numbers
• Multiplying and dividing positive fractions and mixed numbers
• Combined operations on positive and negative fractions and mixed numbers

Rational Numbers

A rational number is a number which can be expressed as a fraction. Some examples of rational numbers are as follows:

Proper Fractions:

A proper fraction is when the value of the numerator is smaller than that of the denominator. 

Improper Fractions:

An improper fraction is when the value of the denominator is bigger than that of the numerator. 

Mixed Numbers:

Improper fractions are expressed as the sum of an integer and a proper fraction.

Example:

  $\begin{align*} 1\frac13 &= 1 + \frac13\\ &= \frac33 + \frac13 \\ &= \frac43\end{align*}$

Negative Rational Numbers

Both $\begin{align} \frac{-3}{4} \end{align}$ or $\begin{align} \frac{3}{-4} \end{align}$ will simplify to give us  $\begin{align} -\frac{3}{4} \end{align}$.

This is because a negative integer divided by a positive integer would give a negative value. Likewise, a positive integer divided by a negative integer would also give a negative value.

Similarly, if we rewrite the mixed number $\begin{align} -1\frac{1}{4} \end{align}$ into an improper fraction, it will gives us $\begin{align} -\frac{5}{4} \end{align}$ , in which it can be rewritten as  $\begin{align} \frac{-5}{4} \end{align}$ or $\begin{align} \frac{5}{-4} \end{align}$.

1. Addition and subtraction of positive and negative fractions and mixed numbers 

Let’s understand this with the help of some examples:

Question 1:

Without using a calculator, evaluate the following.

1. $\begin{align} \frac{1}{3}+(-\frac{1}{4}) \end{align}$
2. $\begin{align} -\frac{2}{5}-(-\frac{1}{2})\\ \end{align}$
3. $\begin{align} -3\frac{1}{2}+(-\frac{1}{3}) \end{align}$
4. $\begin{align} 1\frac{1}{2}+(-2\frac{1}{3}) \end{align}$

Solution: 

1. 

$\begin{align*} & \frac13+(-\frac14)\\ &=\frac13-\frac14\\ &=\frac{4(1)\;-\;3(1)}{12}\\ &=\frac{4 -3}{12}\\ &=\frac1{12} \end{align*}$

2.

$\begin{align*} & -\frac25-(-\frac12)\\&=-\frac25+\frac12\\ &=-\frac25+\frac12\\ &=\frac{2 (-2) + 5 (1)}{10}\\ &=\frac{-4+5}{10}\\ &=\frac{1}{10} \end{align*}$

3.

$\begin{align*} & -3\frac12+(-\frac13)\\&=-\frac72-\frac13\\ &=\frac{-7}{2}-\frac13\\ &=\frac{3 (-7)\;-\;2 (1)}6\\ &=\frac{-21\;-\;2}6\\ &=\frac{-23}6\\ &=-3\frac56 \end{align*}$

4. 

$\begin{align*} & 1\frac12+(-2\frac13)\\&=\frac32-\frac73\\ &=\frac{3 (3)\;-\;2 (7)}6\\ &=\frac{9\;-\;14}6\\ &=\frac{-5}6\\ &=-\frac56 \end{align*}$

2. Multiplication and Division of fractions and mixed numbers 

Let’s understand this with the help of some examples:

Question 2:

Without using a calculator, evaluate the following.

1. $\displaystyle{\frac23 × (-\frac14)}$
    
2. $\displaystyle{-\frac25 × (-\frac12)\\}$
    
3. $\displaystyle{-3\frac12 × (-\frac13)}$

Solution: 

1.

$\begin{align*} & \frac {2}{3} \times (-\frac {1}{4})\\\\ &= \frac{2 \times (-1)}{3 \times 4} \\\\ &=\frac{-2}{12} \\\\ &=\frac {-1}{6} \\\\ &= -\frac{1}{6} \end{align*}$ 

2. 

 $\begin{align*} & -\frac {2}{5} \times (-\frac {1}{2}) \\\\ & = \frac {-2}{5}\times\frac{-1}{2}\\\\ &= \frac{(-2) \times (-1)}{5 \times 2} \\\\ &=\frac{2}{10} \\\\ &=\frac {1}{5} \\\\ \end{align*}$

3.

 $\begin{align*} &-3\frac {1}{2} \times (-\frac {1}{3}) \\\\ &= -\frac{7}{3}\times (-\frac{1}{3})\\\\ &=\frac{(-7) \times (-1)}{2 \times 3} \\\\ &=\frac{7}{6} \\\\ &= 1\frac{1}{6} \end{align*}$