Theory:

The reciprocal of a number is one divided by that number. Formally the reciprocal of \(x =\) 1x.
So, for example, the reciprocal of \(5\) is one quarter: The reciprocal of \(5\) is 15.
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If 18 is number then, the reciprocal of 18 is \(8\).
 
Important!
Rational Number: A number can be made by dividing two integers.
  • An integer is a number with no fractional part.
Example:
0.5 is a rational number because 0.5 \(=\)  32  (3 and 2 are both integers.)
When 158 is a rational number then, the reciprocal of 158 is 815, to get the product as \(1\)? 
 
Thus, 158 \(×\) 815 \(=\) \(1\).
 
Similarly, 49 must be multiplied by 94 so as to get the product as \(1\).
 
We state that 158 is the reciprocal of 815 and 49 is the reciprocal of 94.
 
Can you guess what is the reciprocal of \(0\)?
 
Important!
Is there a rational number which when multiplied by \(0\) give \(1\)? Thus, zero has no reciprocal.
We state that a rational number cd is called the reciprocal or multiplicative inverse of another non-zero rational number ab if ab \(×\) cd \(=\) \(1\).