1680 can be divided by all three.
1680
560 (1680 divided by 3)
1680 divided by 4 is equivalent to 420.
240 x 7 = 1680
16800
840, 1680, 3360 and so on.
0.0036
15/560 - 100/84 = (15*3 -100*20)/1680 = (45-2000)/1680 = -1955/1680 = -391/336 or -1.164
0.0238
1680 and its multiples.
1680