Answer:
The strands change color at the same time again after 90 seconds
Step-by-step explanation:
We are told:
Strand 1: changes between red and blue every 15 seconds.
Strand 2: changes between green and gold every 18 seconds.
To solve for this question, we use the LCM method.
Step 1
List multiples of each number until the first common multiple is found.
Multiples of 15:
15, 30, 45, 60, 75, 90, 105, 120
Multiples of 18:
18, 36, 54, 72, 90, 108, 126
Therefore,
LCM(15, 18) = 90
The first common multiple is 90, and this is the lowest common multiple.
Therefore, the strands will change color at the same time again after 90 seconds.
