Q19 ARITHMETIC PROBLEMS
N persons stand on the circumference of a circle at distinct points. Each possible pair of persons, not standing next to each other, sings a two-minute song one pair after the other. If the total time taken for singing is 28 minutes, what is N?
Total number of pairs is N C 2.
Number of pairs standing next to each other = N.
Therefore, number of pairs in question = N C 2- N = 28/2 = 14.
If N = 7,
7C 2- 7 = 21 - 7 = 14.
N = 7....Write Here