Step 1: Recall the formula for the common difference. In an arithmetic progression (A.P.), the common difference is given by: \[ d = a_2 - a_1 \] Step 2: Substitute the values. The first term \(a_1 = 2\) and the second term \(a_2 = 4\). \[ d = 4 - 2 = 2 \] Step 3: Conclusion. Hence, the common difference of the given A.P. is 2. Final Answer: \[ \boxed{d = 2} \]