Correct Answer: (a) 15 - 220 - 215
Solution:Logic : {n : n² : n² - 5}
(15, 220, 215) ⇒ (15 : 15² = 220 : 15² - 5 = 215)
(10, 100, 95) ⇒ (10 : 10² = 100 : 10² - 5 = 95)
(20, 400, 395) ⇒ (20 : 20² = 400 : 20² - 5 = 395)
(25, 625, 620) ⇒ (25 : 25² = 625 : 25² - 5 = 620)
Hence we can see that all are following the same pattern except (15, 220, 215).