Chapter 12 changing time of class 4 is to encourage the students to interact with the elders and know about their livelihood when they were children. Chapter 12 teaches children to compare the differences between different periods. For the comparison, factors like the materials used in building a house, the amount spent on building a house, etc. are considered. It also teaches us about the processes involved in the construction of a building or a house. Students are expected to do research by going to a construction site under the elderly assistance and accumulate the necessary information regarding the processes involved in constructing a building. All the study materials are in PDF format and easy to download.