Theory:

     He was a round little man with a red face and a whole box of tools with dials and wires. He smiled at Margie and gave her an apple, then took the teacher apart. Margie had hoped he wouldn’t know how to put it together again, but he knew how all right, and, after an hour or so, there it was again, large and black and ugly, with a big screen on which all the lessons were shown and the questions were asked. That wasn’t so bad. The part Margie hated most was the slot where she had to put homework and test papers. She always had to write them out in a punch code they made her learn when she was six years old, and the mechanical teacher calculate the marks in no time.
Explanation:
 
Here they are giving the details of the County Inspector who came to check the mechanical teacher. He looks like a round little man with a red face. He was carrying a big box full of tools with dials and wires. This man took the machine to repair it. Margie desired that he should not be able to repair the computer. She did not like to study from the mechanical teacher, but the man was a skill full, and within an hour, he had repaired the computer and made it ready to teach Margie once again. Margie narrates the computer to be huge, black in colour and unpleasant. It has a screen, and all the lessons appear on the screen, and many questions are asked. Margie hated this mechanical teacher the most because she had to submit her homework and test papers to it. Margie had to write her homework and test papers in a particular punch code which is a computing language. She had learned it when she was \(6\) yrs old. The machine used to check the papers and calculate her marks so soon.
 
Meanings of difficult words:
 
Numbers
Word
Meaning
1.
SlotA given space, time, or, position.
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.