Problema Solution
Rhianna has 3 sets of lights. The first set turn on ans stay on for five seconds and then turn off and stay off for five seconds. The second set turn on, stay on for 4 seconds and then turn off for 4 seconds. The 3rd set turn on, stay on for 3/4 second and then turn off for 3/4 of a second. She switches them on at the same time. How long will it be before all three sets are on at the same time?
Answer provided by our tutors
we need to find the least common multiple of 2*4, 2*5 and 2*3/4 that is the least common multiple of 8,10 and 3/2
least common multiple for 8 and 10 is 40
the least common multiple of 40 and 3/2 is 120 since
120 = 3*40
120 = 80*3/2
thus after 120 second all the lights on the set will be on.