One light changes at 28 seconds the other at 32 how long before they both change together?

To find when both lights change together, we first need to determine the least common multiple (LCM) of their change intervals. The first light changes every 28 seconds, and the second every 32 seconds. The LCM of 28 and 32 is 224 seconds. Therefore, both lights will change together again in 224 seconds.