Question:

The regular mathematics faculty could not teach because of being sick. As a stop-gap arrangement, different visiting faculty taught different topics on 4 different days in a week. The scheduled time for class was 7:00 am, with a maximum permissible delay of 20 minutes. The monsoon made the city bus schedules erratic, so the classes started at different times on different days.

Mr. Singh did not teach on Thursday. Calculus was taught in the class that started at 7:20 am. Mr. Chatterjee took the class on Wednesday, but he did not teach probability. The class on Monday started at 7:00 am, but Mr. Singh did not teach it. Mr. Dutta did not teach ratio and proportion. Mr. Banerjee, who did not teach set theory, taught a class that started five minutes later than the class in which probability was taught. The teacher in Friday's class taught set theory. Wednesday's class did not start at 7:10 am. No two classes started at the same time.

78. The option which gives the correct teacher-subject combination is:

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Work out which day Mr. Singh teaches first (it has to be Friday), then use the clue that Friday's teacher taught set theory to fix his subject directly.
Updated On: Jul 10, 2026
  • Mr. Chatterjee - ratio and proportion
  • Mr. Banerjee - calculus
  • Mr. Chatterjee - set theory
  • Mr. Singh - set theory
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The Correct Option is D

Solution and Explanation

Step 1: Place Mr. Chatterjee and Mr. Singh on their days.
Mr. Chatterjee is stated to be on Wednesday. Mr. Singh does not teach on Thursday and does not teach the Monday class (given directly), and Wednesday is already taken by Mr. Chatterjee, so Mr. Singh is left with Friday.

Step 2: Read off Mr. Singh's topic from the Friday clue.
The teacher in Friday's class taught set theory, so Mr. Singh taught set theory. This rules out any option that pairs Mr. Singh with calculus.

Step 3: Find who taught probability, to clear Mr. Chatterjee's topic.
Mr. Chatterjee did not teach probability (given), and cannot teach set theory since that belongs to Mr. Singh. Mr. Banerjee is also ruled out of probability, because his class started five minutes after the probability class, so he is a different person from the probability teacher. That leaves Mr. Dutta as the probability teacher, placed on Monday at 7:00 am, since putting him on Thursday would push the probability class before 7:00 am.

Step 4: Split ratio and proportion and calculus between Mr. Chatterjee and Mr. Banerjee.
Calculus starts at 7:20 am. Mr. Banerjee's class, on Thursday, starts at 7:05 am (five minutes after Mr. Dutta's 7:00 am Monday class), so Mr. Banerjee cannot be the calculus teacher; he teaches ratio and proportion. That leaves calculus for Mr. Chatterjee on Wednesday, at 7:20 am.

Final Answer:
Putting it together: Mr. Dutta - probability, Mr. Chatterjee - calculus, Mr. Banerjee - ratio and proportion, Mr. Singh - set theory. So Mr. Chatterjee - ratio and proportion is wrong (he taught calculus), Mr. Banerjee - calculus is wrong (he taught ratio and proportion), Mr. Chatterjee - set theory is wrong (set theory belongs to Mr. Singh), and Mr. Singh - set theory is exactly right. \[ \boxed{\text{Mr. Singh - set theory}} \]
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