Age of Information (AoI) has been studied recently for satisfying the timeliness requirements of the emergent applications, i.e. smart cities and smart wearables in future Internet of Everything (IoE). In order to integrate multiple information flows i wireless powered sensor network (WPSN), we propose age of sensing (AoS) for measuring freshness of the fused information, which is defined as the time elapsed from the generation moment of the sensing information used for generating the fresh reliable fused information. Specifically, a wireless power transfer (WPT) aided wireless sensor network (WSN) is studied. Multiple batteryless sensors cooperatively sense common objects and then timely upload the sensing information to a fusion center (FC). The FC fuses the correctly decoded information from different sensors and finally evaluates the reliability of the fused information. The number of time slots for WPT and the deployment of the sensors are then jointly optimised, in order to minimise the average AoS. A Fibonacci aroused integer programming approach is then proposed to solve the nonlinear integer problem having NP-hard complexity. Simulation results validate the accuracy of the theoretical analysis for the AoS, while also demonstrating that our algorithm achieves the superb performance by referring to the optimal exhaustive method.