Answer: The correct option is
(C) 28th lamp post.
Step-by-step explanation: Given that for a 4th July parade, every 4th lamp post has red and white balloons and every 7th lamp post has blue and white balloons.
We are to select the number of lamp post that will have red, white and blue balloons.
Since every 4th lamp post has red and white balloons and every 7th lamp post has blue and white balloons, so
the number of lamp post that will have all red, white and blue balloons will be the LCM of 4 and 7.
That is,
LCM (4, 7) = 4 × 7 = 28.
Thus, the 28th lamp post will have red, white and blue balloons.
Option (C) is CORRECT.
