Theory:

If denominators are not the same, then firstly convert the rational numbers with the same denominators.
Example:
Write the first five rational number between 12 and 45.
Given: 12 and 45.
To find the five rational number between 12 and 45.
Step 1: Make a denominator as same.
  
 12 \(=\) 1×52×5 \(=\) 510.
   
45 \(=\) 4×25×2 \(=\) 1210.
 
Step 2: Since we need to find five rational number, multiply and divide by \(6\)
 
5×610×6 \(=\) 3060
 
12×610×6 \(=\) 7260
 
Therefore, the rational number between  510 \(=\) 12 and 1210 \(=\) 45 are 3160, 3260, 3360, 3460, 3560, ................................... 7260.
 
(Note: This again shows that there are many rational numbers between any two given rational numbers).
 
In this, the first five rational numbers are 3160, 3260, 3360, 3460, 3560.