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Lights of four colors (red, blue, green, yellow) are hung on a ladder. On every step of the ladder there are two lights. If one of the lights is red, the other light on that step will always be blue. If one of the lights on a step is green, the other light on that step will always be yellow. Which of the following statements is not necessarily correct? (A) The number of red lights is equal to the number of blue lights (B) The number of green lights is equal to the number of yellow lights (C) The sum of the red and green lights is equal to the sum of the yellow and blue lights (D) The sum of the red and blue lights is equal to the sum of the green and yellow lights

1. The number of red lights is equal to the number of blue lights
2. The number of green lights is equal to the number of yellow lights
3. The sum of the red and green lights is equal to the sum of the yellow and blue lights
4. The sum of the red and blue lights is equal to the sum of the green and yellow lights

Correct answer: The sum of the red and blue lights is equal to the sum of the green and yellow lights

Solution

This option is correct because the pairing rules dictate that every red light must have a blue light, and every green light must have a yellow light, ensuring that the total counts of red and blue lights will always match the total counts of green and yellow lights.

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