What are the five common multiples of 7 and 20?

Answer 1

All multiples of the lowest common multiple of two numbers are common multiples of both the numbers; lcm(7, 20) = 140 → their (infinitely many) common multiples are the multiples of 140, namely:

140, 280, 420, 560, 700, 840, 980, 1120, 1260, 1400, 1540, 1680, 1820, 1960, 2100, 2240, 2380, 2520, 2660, 2800, 2940, 3080, 3220, 3360, 3500, 3640, 3780, 3920, 4060, 4200, 4340, 4480, 4620, 4760, 4900, 5040, 5180, 5320, 5460, 5600, 5740, 5880, 6020, 6160, 6300, 6440, 6580, 6720, 6860, 7000, 7140, 7280, 7420, 7560, 7700, 7840, 7980, 8120, 8260, 8400, 8540, 8680, 8820, 8960, 9100, 9240, 9380, 9520, 9660, 9800, 9940, 10080, 10220, 10360, 10500, 10640, 10780, 10920, 11060, 11200, 11340, 11480, 11620, 11760, 11900, 12040, 12180, 12320, 12460, 12600, 12740, 12880, 13020, 13160, 13300, 13440, 13580, 13720, 13860, 14000, ...

Pick any 5 of them.