Question

# The product of a rational number with its reciprocal is$\left( a \right)0 \\ \left( b \right)1 \\ \left( c \right) - 1 \\ \left( d \right){\text{None of these}} \\$

Hint: A rational number is a number that can be expressed as the quotient of fraction $\dfrac{p}{q}$ of two integers, a numerator p and a non-zero denominator q.

We know rational numbers can be expressed in the form of $\dfrac{p}{q}$ .
Rational number $= \dfrac{p}{q}.................\left( 1 \right)$
Now, the reciprocal of $\dfrac{p}{q}$ is $\dfrac{q}{p}$ .
Reciprocal of rational number $= \dfrac{q}{p}.................\left( 2 \right)$
Now the product of a rational number with its reciprocal,
Multiply (1) and (2) equations
$\left( {{\text{Rational number}}} \right) \times \left( {{\text{Reciprocal of rational number}}} \right) = \dfrac{p}{q} \times \dfrac{q}{p} = 1$
The product of a rational number with its reciprocal is 1.
So, the correct option is (b).

Note: Whenever we face such types of problems we use some important points. As we know, a rational number can be expressed in the form of $\dfrac{p}{q}$ and its reciprocal is $\dfrac{q}{p}$ . So, it is a proven product of rational numbers and its reciprocal always be 1.