The wheels revolve round a common horizontal axis. They make 15, 20 and 48 revolutions in a minute respectively. Starting with a certain point on the circumference down wards. After what interval of time will they come together in the same position?
Correct answer: A. 1 min
- A. 1 min
- B. 2 min
- C. 3 min
- D. None
Explanation
After t minutes, the wheels make 15t, 20t and 48t revolutions. They are all back at the original position when these three quantities are whole numbers; the first such time is t = 1 minute, giving 15, 20 and 48 complete revolutions. The likely mistake is option b, which waits for two minutes even though all three wheels already coincide after one minute.
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Sequences describe ordered terms formed by a pattern, while series represent the sum of those terms. Questions cover arithmetic and geometric sequences, their nth terms, common difference or ratio, finite sums, and applications, with the sequence itself kept distinct from the corresponding series.
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