Answer:
4620
Explanation:
Multiples of 308:
308, 616, 924, 1232, 1540, 1848, 2156, 2464, 2772, 3080, 3388, 3696, 4004, 4312, 4620, 4928, 5236
Multiples of 420:
420, 840, 1260, 1680, 2100, 2520, 2940, 3360, 3780, 4200, 4620, 5040, 5460
Therefore,
LCM(308, 420) = 4620