Theory:

     “May be,” he said nonchalantly. He walked away whistling, the dusty old book tucked beneath his arm.
 
     Margie went into the schoolroom. It was right next to her bedroom, and the mechanical teacher was on and waiting for her. It was always on at the same time every day except Saturday and Sunday, because her mother said little girls learned better if they learned at regular hours.
 
     The screen was lit up, and it said: “Today's arithmetic lesson is on the addition of proper fractions. Please insert yesterday’s homework in the proper slot."
Explanation:
 
Tommy tried not to pay attention to her and said that perhaps she could read it. Tommy was feeling very proud because Margie was interested in reading the book. He placed the book under his arm, and he went off to his home.
 
Margie went to her school. It was the next room, a virtual classroom. There was a machine teacher for Margie. It was on, and it was waiting for her to begin teaching her. Margie uses to study all the weekdays except Saturdays and Sundays. Margie’s mother was very concerned about this as she felt Margie would learn better if she would study every day at the same time.
 
Margie sat in front of the machine. It said that the lesson for the day was in Arithmetic and the topic was the addition of proper fractions. It also instructed her to insert the homework of the previous day in the proper slot.
 
Meanings of difficult words:
 
Numbers
Word
Meaning
1.
NonchalantlyNot showing much interest or enthusiasm; carelessly.
Reference:
State Council of Educational Research and Training (2018). Term-1 English Standard-9. The fun they had - Isaac Asimov (pp. 150-153). Published by the Tamil Nadu Textbook and Educational Services Corporation.