Periodic signals are those which repeat itself after certain interval of time. The time after which it repeats is called as the period of the signal. Periodic signals are used almost everywhere in application of electrical engineering such as, supply of electricity means supplying AC voltage constantly. This supply of ac is periodic waveform [1]. Continuous time sinusoids are periodic if they are not truncated and period of this type of signal can be predicted in advanced just comparing the angular frequency (w). Whenever addition or multiplications of two or more sinusoids or any other continuous time signals are involved then it is not that simple to find the period of the resulting signal [2]. All the cases of addition and multiplication of different types of continuous time signals were taken into account and the result were obtained from MATLAB. Findings were analyzed and generalized being based on the result obtained from MATLAB. When addition of two or more continuous time signals takes place, the period of resulting signal is the Least Common Multiple (LCM) of the period of individual signal. When multiplication of two or more continuous time signal are involved the period of resulting signal is the half the value of Least Common Multiple (LCM) of the period of individual signal, if any one of the signal has both positive and negative amplitude. Else the period of the resulting signal is Least Common Multiple of the period of individual signal. When addition of two or more continuous time signal are involved the period of resulting signal is the value of Least Common Multiple (LCM) of the period of individual signal, even if any one of the signal has both positive and negative amplitude. Generally Continuous time Fourier series is performed to obtain the spectrum either that may be magnitude spectra or phase spectra. Periodicity and the period of the signal are vital for representing time domain signal to frequency domain.