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.

80. The option which gives a possible correct class time - week day combination is:

Show Hint

Wednesday and Thursday are fully fixed by the calculus and five-minutes-after-probability clues; only Friday has some room, so match those two fixed values first.
Updated On: Jul 10, 2026
  • Wednesday - 7:10 am, Thursday - 7:20 am, Friday - 7:05 am
  • Wednesday - 7:20 am, Thursday - 7:15 am, Friday - 7:20 am
  • Wednesday - 7:05 am, Thursday - 7:20 am, Friday - 7:10 am
  • Wednesday - 7:20 am, Thursday - 7:05 am, Friday - 7:10 am
Show Solution
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The Correct Option is D

Solution and Explanation

Step 1: Fix Wednesday's start time.
As worked out from the teacher clues, Mr. Chatterjee (Wednesday) ends up teaching calculus, and calculus starts at 7:20 am. So Wednesday's class started at 7:20 am. This already removes any option that gives Wednesday a different time, such as 7:10 am or 7:05 am.

Step 2: Fix Thursday's start time.
Mr. Banerjee is on Thursday, and his class starts five minutes after the probability class. The probability class (Mr. Dutta, Monday) starts at 7:00 am, so Mr. Banerjee's Thursday class starts at 7:00 am + 5 minutes = 7:05 am. This rules out any option that gives Thursday 7:20 am or 7:15 am.

Step 3: Check what is left for Friday.
Mr. Singh is on Friday. The firm times used so far are Monday 7:00 am, Wednesday 7:20 am and Thursday 7:05 am, all different, so no two classes clash. Friday's time is not pinned down by any further clue beyond no two classes starting at the same time, so it can be any of the remaining permitted values, such as 7:10 am or 7:15 am; the question only asks for a possible correct combination, not the one forced combination.

Step 4: Match against the options.
Only the combination Wednesday 7:20 am, Thursday 7:05 am, Friday 7:10 am has both Wednesday and Thursday matching the values that are actually forced by the clues, with Friday taking one of its two open values. Every other option gets Wednesday or Thursday wrong, or repeats a time already used elsewhere, for example pairing Wednesday 7:20 am with Friday 7:20 am would mean two classes start at the same time, which the puzzle forbids.

Final Answer:
Wednesday 7:20 am, Thursday 7:05 am, Friday 7:10 am is the combination consistent with all the clues. \[ \boxed{\text{Wednesday 7:20, Thursday 7:05, Friday 7:10}} \]
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