Let the total number of students be n. For each pair, two cards are sent and the total number of pairs can be nC2 So, total cards = 2 x nC2 or 2 x nC2 = 1980,= 2 x n(n-1)/21 = 1980∴ n² - n = 1980or n² - 45n + 44n - 1980 = 0or n(n - 45) + 44(n - 45) = 0or (n + 44) (x - 45) = 0∴ n = 45, - 44 (Now, discard - value)∴ n = 45
EXAMIANS