Question

11,20,57,280 ______series​

Answer 1

(12 * 1) - 1 = 11

(11 * 2) - 2 = 20

(20 * 3) - 3 = 57

(57 * 4) - 4 = 224

(224 * 5) - 5 = 1115

(1115 * 6) - 6 = 6684.

Therefore the next number in the series is 6684.