Based on the seconds that Stoplight A and Stoplight B take to change color, the number of seconds till they change color at the same time is 30 seconds.
To find out the time that both stoplights will change color at the same time, you need to look for the lowest common multiple of 18 and 15.
The multiples of 15 are:
15, 30, 45, 60, 75, 90, 105
The multiples of 18 are:
18, 36, 54, 72, 90
The lowest common multiple is 90 seconds.
Because the lights changed color 60 seconds ago, the time till they change at the same time is:
= 90 - 60
= 30 seconds
Find out more on the lowest common multiple at https://brainly.com/question/16054958
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