Question

Three wheels can complete 60, 36, 24 revolutions per minute respectively. There is a spot on each wheel that touches the ground at time zero. After how much time, all these spots will simultaneously touch the ground again.

• A. $\frac{5}{2}s$
• B. $\frac{5}{3}s$
• C. $5s$
• D. $7.5s$

Answer 1

The correct option is C $5s$

Three wheels can complete 60, 36, 24 revolutions per minute.
Three wheels can complete 1, 0.6, 0.4 revolutionsper second.
Time to complete one revolution - 1, 5/3, 5/2 secs.
LCM of 1, 5/3 and 5/2 is 5.
After 5 mins, all these spots will simultaneously touch the ground again.