It depends on what that is.
312 : 624 is a ratio.
3 : 12 = 6 : 24 is a proportion.
312 of course.
It is a factor of 624.
624 is divisible by 312.
The numbers that are divisible by 312 are infinite. Four of them are: 312, 624, 936, 1248.
624
624 / 2 = 312 312 - 292 = 20
312, 624, 936 and so on.
78, 156, 234, 312, 390, 468, 546, 624, 702, . . . 104, 208, 312, 416, 520, 624, 728, 832, 936, . . .
78, 156, 234, 312, 390, 468, 546, 624, 702, 780, 858, . . .104, 208, 312, 416, 520, 624, 728, 832, 936, 1040, 1144, . . .
208 312 416 520 624 728 832
(312)/(2 and 1/2) = (312)/(5/2) = (312x2)/5 = 624/5 = 124 and 4/5 hours
312