An antique grandfather's clock, which gains uniformly, is 10 minutes slow at 9:00 a.m. in the morning on Monday and 10 minutes 48 seconds fast at 9:00 p.m. on the following Monday. When was it correct?

The clock goes from 10 minutes slow to 10 minutes 48 seconds fast, meaning it gains a total of 20 minutes and 48 seconds over the week. Converting this to seconds gives a total gain of 1248 seconds over exactly 181 hours. To find when it was correct, we calculate when it gained the initial 10 minutes (600 seconds), setting up the proportion 1248 / 181 = 600 / x. Solving for x gives approximately 87.019 hours after Monday at 9:00 am, which places the correct time late Thursday evening. The result is 11 p.m. 32 minutes, Thursday.

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